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1

Numerical simulation for fan broadband noise prediction  

NASA Astrophysics Data System (ADS)

In order to elucidate the broadband noise of fan, the numerical simulation of fan operating at two different rotational speeds is carried out using the three-dimensional unsteady Reynolds-averaged Navier-Stokes (URANS) equations. The computed results are compared to experiment to estimate its accuracy and are found to show good agreement with experiment. A method is proposed to evaluate the turbulent kinetic energy in the framework of the Spalart-Allmaras one equation turbulence model. From the calculation results, the turbulent kinetic energy is visualized as the turbulence of the flow which leads to generate the broadband noise, and its noise sources are identified.

Hase, Takaaki; Yamasaki, Nobuhiko; Ooishi, Tsutomu

2011-03-01

2

Numerical simulation for fan broadband noise prediction  

Microsoft Academic Search

In order to elucidate the broadband noise of fan, the numerical simulation of fan operating at two different rotational speeds\\u000a is carried out using the three-dimensional unsteady Reynolds-averaged Navier-Stokes (URANS) equations. The computed results\\u000a are compared to experiment to estimate its accuracy and are found to show good agreement with experiment. A method is proposed\\u000a to evaluate the turbulent kinetic

Takaaki Hase; Nobuhiko Yamasaki; Tsutomu Ooishi

2011-01-01

3

Ray theory to predict the propagation of broadband fan noise  

Microsoft Academic Search

The feasibility of using a ray theory approach to predict the propagation, attenuation and radiation of high frequency engine intake noise is illustrated. Good agreement is demonstrated between ray theory and mode theory predictions for the broadband noise radiated in the absence of flow from short cylindrical ducts and from ducts of slowly varying cross sectional area. The two prediction

A. J. Kempton

1980-01-01

4

Broadband Fan Noise Prediction System for Turbofan Engines, Volume 3.  

National Technical Information Service (NTIS)

Pratt & Whitney has developed a Broadband Fan Noise Prediction System (BFaNS) for turbofan engines. This system computes the noise generated by turbulence impinging on the leading edges of the fan and fan exit guide vane, and noise generated by boundary-l...

B. L. Morin

2010-01-01

5

Broadband Fan Noise Prediction System for Turbofan Engines, Volume 2.  

National Technical Information Service (NTIS)

Pratt & Whitney has developed a Broadband Fan Noise Prediction System (BFaNS) for turbofan engines. This system computes the noise generated by turbulence impinging on the leading edges of the fan and fan exit guide vane, and noise generated by boundary-l...

B. L. Morin

2010-01-01

6

Broadband Fan Noise Prediction System for Turbofan Engines, Volume 1.  

National Technical Information Service (NTIS)

Pratt & Whitney has developed a Broadband Fan Noise Prediction System (BFaNS) for turbofan engines. This system computes the noise generated by turbulence impinging on the leading edges of the fan and fan exit guide vane, and noise generated by boundary-l...

B. L. Morin

2010-01-01

7

Axial flow fan broad-band noise and prediction  

Microsoft Academic Search

Two prediction methods for broad-band noise of low-pressure axial fans are investigated. Emphasis is put on the interaction noise due to ingested turbulence. The numerical large eddy simulation (LES) is applied to predict the unsteady blade forces due to grid generated highly turbulent inflow; the blade forces are then fed into an analytical two-dimensional acoustic ducted source model. A simple

Thomas Carolus; Marc Schneider; Hauke Reese

2007-01-01

8

Large Eddy Simulations for Fan-OGV Broadband Noise Prediction  

Microsoft Academic Search

The work in this paper forms part of a project on the use of large eddy simulation (LES) for broadband rotor-stator interaction noise prediction. Here we focus on LES of the flow field near a fan blade trailing edge. The first part of the paper aims to evaluate LES suitability for predicting the near-field velocity field for a blunt NACA-0012

Qinling Li; Nigel Peake; Mark Savill

9

The prediction of tonal and broadband slat noise  

NASA Astrophysics Data System (ADS)

Noise from high-lift devices like slats and flaps can contribute significantly to the over-all aircraft sound pressure levels, particularly during approach. The acoustic spectrum of the noise radiated from slats exhibits two distinct features. There is a high-frequency tonal noise component, and a high-energy broadband component ranging from low to mid-frequencies. The objective of this thesis is to predict both tonal and broadband slat noise. An aeroacoustic whistling mechanism is proposed to predict the tonal noise generation. When the vortex shedding frequency at the blunt trailing edge of the slat comes close to one of the normal modes of the gap between the slat and the main element, an intense tonal noise is produced. The normal modes are calculated based on the geometry of the wing. The vortex shedding frequency is predicted based on a linear stability analysis of the slat's wake region. An efficient and robust scheme is developed by which the stability calculation can be performed by a modular algorithm in a relatively quick time. The broadband noise is predicted using a two-step process. First the noise sources are modeled based on the local turbulence information. Then, the sound from these sources is propagated by assuming that the flow past the wing is uniform. A Boundary Element Method is developed to find the Green's function for wave propagation in a moving medium in the presence of the wing. The noise in the far field is then predicted by forming a convolution of the Green's function with the modeled sources. Finally, a technique is presented to account for nonuniform flow around the wing. This requires a solution of the linearized Euler Equations. However, these equations support acoustic as well as instability waves. The instability waves can completely overwhelm the acoustic-wave solution. Thus it is imperative for an accurate noise-prediction scheme to suppress the unwanted instability waves. A detailed mathematical analysis is presented that demonstrates that the instability wave solution is suppressed if the governing equations are solved in the frequency domain. The main focus of this thesis is in the development of numerical schemes and models, and then their use to explore the physics of noise generation, and the prediction of noise radiation, from slats.

Agarwal, Anurag

10

Axial Flow Fan Broad-Band Noise Prediction and Application to Optimum Design  

Microsoft Academic Search

A broad-band noise prediction code based on the work of Carolus et al was written and incorporated into the low-pressure axial fan design program. For the convenience of design calculation, the turbulence statistics were determined by a semi-rational formula for fully-developed duct flow instead of the experiment. The code predicts 3 different forms of broad-band noise that were superimposed to

Jie Zhang; Shaoping Zhou; Jingkuan Ye; Xiaoling Ge; Yongsheng Su

2010-01-01

11

Broadband Noise Predictions for an Airfoil in a Turbulent Stream  

NASA Astrophysics Data System (ADS)

Loading noise is predicted from unsteady surface pressure measurements on a NACA 0015 airfoil immersed in grid-generated turbulence. The time-dependent pressure is obtained from an array of synchronized transducers on the airfoil surface. Far field noise is predicted by using the time-dependent surface pressure as input to Formulation 1A of Farassat, a solution of the Ffowcs Williams - Hawkings equation. Acoustic predictions are performed with and without the effects of airfoil surface curvature. Scaling rules are developed to compare the present far field predictions with acoustic measurements that are available in the literature.

Casper, J.; Farassat, F.; Mish, P. F.; Devenport, W. J.

2003-01-01

12

Ray theory to predict the propagation of broadband fan-noise  

Microsoft Academic Search

The feasibility of using a ray-theory approach to predict the propagation, attenuation, and radiation of high-frequency engine-intake noise is illustrated. Good agreement is demonstrated between ray-theory and mode-theory predictions for the broadband noise radiated in the absence of flow from short cylindrical ducts and from ducts of slowly-varying cross-sectional area. The two prediction schemes are also in broad agreement concerning

A. J. Kempton

1980-01-01

13

On the use of a uniformly valid analytical cascade response function for fan broadband noise predictions  

Microsoft Academic Search

The present paper extends an existing analytical model of the aeroacoustic response of a rectilinear cascade of flat-plate blades to three-dimensional incident vortical gusts, to the prediction of the noise generated by a three-dimensional annular blade-row. The extended formulation is meant to be implemented in a fan broadband noise prediction tool. The intended applications include the modern turbofan engines, for

H. Posson; S. Moreau; M. Roger

2010-01-01

14

A prediction method for broadband shock associated noise from supersonic rectangualr jets  

NASA Astrophysics Data System (ADS)

Braodband shock associated noise is an important aircraft noise component of the proposed high-speed civil transport (HSCT) at take-offs and landings. For noise certification purpose one would, therefore, like to be able to predict as accurately as possible the intensity, directivity and spectral content of this noise component. The purpose of this work is to develop a semi-empirical prediction method for the broadband shock associated noise from supersonic rectangular jets. The complexity and quality of the noise prediction method are to be similar to those for circular jets. In this paper only the broadband shock associated noise of jets issued from rectangular nozzles with straight side walls is considered. Since many current aircraft propulsion systems have nozzle aspect ratios (at nozzle exit) in the range of 1 to 4, the present study has been confined to nozzles with aspect ratio less than 6. In developing the prediction method the essential physics of the problem are taken into consideration. Since the braodband shock associated noise generation mechanism is the same whether the jet is circular or round the present prediction method in a number of ways is quite similar to that for axisymmetric jets. Comparisons between predictions and measurements for jets with aspect ratio up to 6 will be reported. Efforts will be concentrated on the fly-over plane. However, side line angles and other directions will also be included.

Tam, Christopher K. W.; Reddy, N. N.

15

Ray theory to predict the propagation of broadband fan-noise  

NASA Astrophysics Data System (ADS)

The feasibility of using a ray-theory approach to predict the propagation, attenuation, and radiation of high-frequency engine-intake noise is illustrated. Good agreement is demonstrated between ray-theory and mode-theory predictions for the broadband noise radiated in the absence of flow from short cylindrical ducts and from ducts of slowly-varying cross-sectional area. The two prediction schemes are also in broad agreement concerning the variation with wall-impedance of the SPL insertion loss. Several important conclusions are drawn concerning the radiation of broadband noise from cylindrical inlets, from inlets of varying cross-sectional area and from scarfed inlets (for which no modal solution is available). The powerful insight provided by the ray-theory approach is shown to significantly increase understanding of the radiation problem.

Kempton, A. J.

1980-06-01

16

Application of Wake Characteristics to Prediction of Broadband Noise of a Multiblade Fan  

NASA Astrophysics Data System (ADS)

In this study, the wake characteristics of an arc blade were measured by the wind tunnel experiment; the characteristics were defined as the width of the wake, diameter of the vortex, ratio of the vortex scale, and the local lift. The influence of the angle of attack on the aerodynamic noise of the blade was quantitatively predicted by using these characteristics. It was clarified experimentally that the sound pressure of the aerodynamic noise becomes small since the gradient of the differential of the lift fluctuation was reduced according to the increase of the angle of attack. The wake characteristics were applied to the prediction of the broadband noise generated from a multiblade fan; the fan noise level distribution was estimated with high accuracy to be in the range from 1000-3000 Hz and was used to analyze the broadband noise of the fan. From the analysis of the fan noise level, it was found that the difference in the relative velocity caused by the biased internal flow was related to the noise levels.

Sasaki, Soichi; Hayashi, Hidechito

17

Measurement and prediction of broadband noise from large horizontal axis wind turbine generators  

NASA Astrophysics Data System (ADS)

A method is presented for predicting the broadband noise spectra of large wind turbine generators. It includes contributions from such noise sources as the inflow turbulence to the rotor, the interactions between the turbulent boundary layers on the blade surfaces with their trailing edges and the wake due to a blunt trailing edge. The method is partly empirical and is based on acoustic measurements of large wind turbines and airfoil models. Spectra are predicted for several large machines including the proposed MOD-5B. Measured data are presented for the MOD-2, the WTS-4, the MOD-OA, and the U.S. Windpower Inc. machines. Good agreement is shown between the predicted and measured far field noise spectra.

Grosveld, F. W.; Shepherd, K. P.; Hubbard, H. H.

1995-05-01

18

Frequency-domain prediction of broadband trailing edge noise from a blunt flat plate  

NASA Astrophysics Data System (ADS)

The aim of this study is to develop an efficient methodology for frequency-domain prediction of broadband trailing edge noise from a blunt flat plate where non-zero pressure gradient may exist in its boundary layer. This is achieved in two ways: (i) by developing new models for point pressure spectra within the boundary layer over a flat plate, and (ii) by deriving a simple formula to approximate the effect of convective velocity on the radiated noise spectrum. Firstly, two types of point pressure spectra-required as input data to predict the trailing edge noise in the frequency domain-are used. One is determined using the semi-analytic (S-A) models based on the boundary-layer theory combined with existing empirical models. It is shown that the prediction using these models show good agreements with the measurements where zero-pressure gradient assumption is valid. However, the prediction show poor agreement with that obtained from large eddy simulation results where negative (favorable) pressure gradient is observed with the boundary layer. Based on boundary layer characteristics predicted using the large eddy simulations, new model for point wall pressure spectra is proposed to account for the effect of favorable pressure gradient over the blunt flat plate on the wall pressure spectra. Sound spectra that were predicted using these models are compared with measurements to validate the proposed prediction scheme. The advantage of the semi-analytic model is that it can be applied to problems at Reynolds numbers for which the empirical model is not available. In addition, it is expected that the current models can be applied to the cases where favorable pressure gradient exists in the boundary layer over a blunt flat plate. Secondly, in order to quantitatively analyze contributions of the pressure field within the turbulent boundary layer on the flat plate to trailing edge noise, total pressure over the surface of airfoil is decomposed into its two constituents: incident pressure generated in the boundary layer without a trailing edge and the pressure formed by the scattering of the incident pressure at the trailing edge. The predictions made using each of the incident and scattered pressures reveal that the convective velocity of turbulence in the boundary layer dominantly affects the radiated sound pressure spectrum, both in terms of the gross behavior of the overall acoustic pressure spectrum through the scattered pressure and in terms of the narrow band small fluctuations of the spectrum through the incident pressure. The interaction term between the incident and the scattered is defined and the incident is shown to contribute to the radiated acoustic pressure through the interaction term. Based on this finding, a simple model to effectively compute the effects of convection velocities of the turbulence on the radiated sound pressure spectrum is proposed. It is shown that the proposed method can effectively and accurately predict the broadband trailing edge noise from the plate with considering both the incident and the scattered contributions.

Lee, Gwang-Se; Cheong, Cheolung

2013-10-01

19

On the use of a uniformly valid analytical cascade response function for fan broadband noise predictions  

NASA Astrophysics Data System (ADS)

The present paper extends an existing analytical model of the aeroacoustic response of a rectilinear cascade of flat-plate blades to three-dimensional incident vortical gusts, to the prediction of the noise generated by a three-dimensional annular blade-row. The extended formulation is meant to be implemented in a fan broadband noise prediction tool. The intended applications include the modern turbofan engines, for which analytical modelling is believed to be a good alternative to more expensive numerical techniques. The prediction noise model resorts to a strip theory approach based on a three-dimensional rectilinear cascade model. The latter is based on the Wiener-Hopf technique, and yields the pressure field in the blade passage and the unsteady blade loading. The analytical pressure solution is derived by making an extensive use of the residue theorem. The obtained unsteady blade loading distribution over the blades is then used as a dipole source distribution in an acoustic analogy applied in the annular rigid duct with uniform mean flow. The new achievements are then tested on three-dimensional annular-benchmark configurations and compared with three-dimensional lifting-surface models and three-dimensional Euler linearized codes available in the literature. The accuracy of the model is shown for high hub-to-tip ratio cases. When used as such in a true rectilinear-cascade configuration, it also reproduces the exact radiated field that can be derived directly. For low hub-to-tip ratio configurations, the model departs from three-dimensional computations, both regarding the blade loading and the acoustic radiation. A correction is proposed to account for the actual annular dispersion relation in the rectilinear-cascade response function. The results suggest that the proposed correction is necessary to get closer to the underlying physics of the annular-space wave equation, but that it is yet not sufficient to fully reproduce three-dimensional results.

Posson, H.; Moreau, S.; Roger, M.

2010-08-01

20

Open rotor broadband interaction noise  

NASA Astrophysics Data System (ADS)

A theoretical model is presented for calculating the broadband noise produced by the interaction of an open rotor with the wake from either an upstream contra-rotating rotor or a stationary pylon. The model is used to investigate the dependence of the radiated noise on parameters such as pylon–rotor gap and the polar and azimuthal directivity of the noise field. A simple model is also presented which assumes that the unsteady loading on adjacent blades is uncorrelated. It is shown that the simple model can be used to calculate broadband interaction noise for most practical open rotor geometries.

Kingan, Michael J.

2013-08-01

21

Broadband noise prediction when turbulence simulation is available—Derivation of Formulation 2B and its statistical analysis  

NASA Astrophysics Data System (ADS)

We show that a simple modification of Formulation 1 of Farassat results in a new analytic expression that is highly suitable for broadband noise prediction when extensive turbulence simulation is available. This result satisfies all the stringent requirements, such as permitting the use of the exact geometry and kinematics of the moving body, which we have set as our goal in the derivation of useful acoustic formulas for the prediction of rotating blade and airframe noise. We also derive a simple analytic expression for the autocorrelation of the acoustic pressure that is valid in the near and far fields. Our analysis is based on the time integral of the acoustic pressure that can easily be obtained at any resolution for any observer time interval and digitally analyzed for broadband noise prediction. We have named this result as Formulation 2B of Farassat. One significant consequence of Formulation 2B is the derivation of the acoustic velocity potential for the thickness and loading terms of the Ffowcs Williams-Hawkings (FW-H) equation. This will greatly enhance the usefulness of the Fast Scattering Code (FSC) by providing a high-fidelity boundary condition input for scattering predictions.

Farassat, F.; Casper, J.

2012-05-01

22

Application of Wake Characteristics to Prediction of Broadband Noise of a Multiblade Fan  

Microsoft Academic Search

In this study, the wake characteristics of an arc blade were measured by the wind tunnel experiment; the characteristics were defined as the width of the wake, diameter of the vortex, ratio of the vortex scale, and the local lift. The influence of the angle of attack on the aerodynamic noise of the blade was quantitatively predicted by using these

Soichi Sasaki; Hidechito Hayashi

2008-01-01

23

UHB engine fan broadband noise reduction study  

Microsoft Academic Search

A study has been completed to quantify the contribution of fan broadband noise to advanced high bypass turbofan engine system noise levels. The result suggests that reducing fan broadband noise can produce 3 to 4 EPNdB in engine system noise reduction, once the fan tones are eliminated. Further, in conjunction with the elimination of fan tones and an increase in

Philip R. Gliebe; Patrick Y. Ho; Ramani Mani

1995-01-01

24

Localization of aerial broadband noise by pinnipeds  

NASA Astrophysics Data System (ADS)

Although many pinnipeds (seals, sea lions, and walruses) emit broadband calls on land as part of their communication system, few studies have addressed these animals' ability to localize aerial broadband sounds. In this study, the aerial sound localization acuities of a female northern elephant seal (Mirounga angustirostris), a male harbor seal (Phoca vitulina), and a female California sea lion (Zalophus californianus) were measured in the horizontal plane. The stimulus was broadband white noise that was band pass filtered between 1.2 and 15 kHz. Testing was conducted in a hemi-anechoic chamber using a left/right forced choice procedure to measure the minimum audible angle (MAA) for each subject. MAAs were defined as half the angular separation of two sound sources bisected by a subject's midline that corresponded to 75% correct discrimination. MAAs were 4.7°, 3.6°, and 4.2° for the northern elephant seal, harbor seal, and California sea lion, respectively. These results demonstrate that individuals of these pinniped species have sound localization abilities comparable to the domestic cat and rhesus macaque. The acuity differences between our subjects were small and not predicted by head size. These results likely reflect the relatively acute general abilities of pinnipeds to localize aerial broadband signals.

Holt, Marla M.; Schusterman, Ronald J.; Southall, Brandon L.; Kastak, David

2004-05-01

25

Discrete-frequency and broadband noise radiation from diesel engine cooling fans  

Microsoft Academic Search

This effort focuses on measuring and predicting the discrete-frequency and broadband noise radiated by diesel engine cooling fans. Unsteady forces developed by the interaction of the fan blade with inlet flow are the dominant source for both discrete-frequency and broadband noise of the subject propeller fan. In many cases, a primary source of discrepancy between fan noise prediction and measurement

Geon-Seok Kim

2007-01-01

26

Main rotor broadband noise study in the DNW  

NASA Astrophysics Data System (ADS)

An acoustics test of a 2/5 scale model BO-105 helicopter main rotor was conducted in the Duits-Nederlandse Windtunnel (DNW). A range of operating conditions was tested from hover to moderately high flight speeds for various climb and descent rates at different thrust settings. Diagnostic tests including rotor speed and blade geometry changes were made to better isolate and study particular broadband self noise sources. Acoustic data in the form of acoustic pressure time histories and power spectra are used to demonstrate the regions of importance of the different broadband noise sources and their sensitivity to operating conditions. To help interpret the data, comparisons are made to predictions of rotor broadband noise. The predictions are based on self noise data previously obtained from isolated airfoil sections and the use of the NASA ROTONET program to define rotor performance and to sum contributions of noise from individual blade segments. An important result herein is the identification and articulation of a previously unheralded rotor broadband noise source. This source is blade-turbulent wake interaction (BWI) noise which dominates the spectra in the mid-frequencies for off-peak blade-vortex interaction (BVI) noise flight conditions.

Brooks, Thomas F.; Marcolini, Michael A.; Pope, D. Stuart

1987-02-01

27

A study of rotor broadband noise mechanisms and helicopter tail rotor noise  

NASA Astrophysics Data System (ADS)

A study is made of the relative problems of rotor broadband noise mechanisms and helicopter tail rotor noise. The rotor broadband noise mechanisms considered are: (1) lift fluctuation due to turbulence ingestion, (2) boundary layer/trailing edge interaction, (3) tip vortex formation, and (4) turbulent vortex shedding from blunt trailing edge. Predictions are compared to available experimental data and show good agreement. The study shows that inflow turbulence is the most important broadband noise source for typical helicopters' main rotors at low- and mid-frequencies. Trailing edge noise and tip vortex noise are found to be important at high frequencies; they are also very sensitive to rotor blade angle of attack. Trailing edge thickness noise is also very important; it generates a large spectrum hump, and is very sensitive to any change of the trailing edge thickness.

Chou, Shau-Tak Rudy

28

Aircraft Noise Prediction Program (ANOPP) Fan Noise Prediction for Small Engines.  

National Technical Information Service (NTIS)

The Fan Noise Module of ANOPP is used to predict the broadband noise and pure tones for axial flow compressors or fans. The module, based on the method developed by M. F. Heidmann, uses empirical functions to predict fan noise spectra as a function of fre...

J. W. Hough D. S. Weir

1996-01-01

29

Sound localization of aerial broadband noise in pinnipeds  

NASA Astrophysics Data System (ADS)

Pinnipeds (seals, sea lions, and walruses) emit broadband calls on land as part of their communication system in order to coordinate their reproductive activities. How well do they localize these types of signals? In this study, the aerial sound localization acuities of a harbor seal (Phoca vitulina), a California sea lion (Zalophus californianus), and a northern elephant seal (Mirounga angustirostris) were measured in the horizontal plane with a broadband white noise stimulus. Testing was conducted in a hemi-anechoic chamber using a left/right forced choice procedure to measure the minimum audible angle (MAA) for each subject. MAAs were defined as half the angular separation of two sound sources relative to a subject's midline that corresponded to 75% correct discrimination. MAAs were 3.6, 4.2, and 4.7 deg for the harbor seal, California sea lion, and northern elephant seal, respectively. These results demonstrate that these pinniped species had sound localization abilities comparable to the domestic cat and rhesus macaques. The acuity differences between our subjects were small, were not predicted by head size, and therefore likely reflect the relatively acute abilities of other pinniped species to localize aerial broadband signals.

Holt, Marla M.; Schusterman, Ronald J.; Kastak, David; Southall, Brandon L.

2003-04-01

30

Broad-band colored noise: digital simulation and dynamical effects.  

PubMed

We propose a broad-band colored noise, which allows the transition between "red" and "green" noises. A double-integral algorithm for solving the Langevin equation with this noise is developed. The steady currents of an overdamped particle moving in the correlation and diffusion ratchets are calculated. It is shown that the flow reverses sign when the external noise is filtered off in the region of low frequencies to a sufficient extent. The present noise is also compared with the Ornstein-Uhlenbeck colored noise and the harmonic noise. PMID:11970712

Bao, J D; Liu, S J

1999-12-01

31

The flux-dependent amplitude of broadband noise variability in X-ray binaries and active galaxies  

Microsoft Academic Search

Standard shot-noise models, which seek to explain the broadband noise variability that characterizes the X-ray light curves of X-ray binaries and active galaxies, predict that the power spectrum of the X-ray light curve is stationary (i.e. constant amplitude and shape) on short time-scales. We show that the broadband noise power spectra of the black hole candidate Cyg X-1 and the

Philip Uttley; Ian M. McHardy

2001-01-01

32

Wave propagation effects of broadband electrostatic noise in the magnetotail  

NASA Astrophysics Data System (ADS)

An analysis of the wave and particle data from ISEE 1 for 1978 yielded several examples of crossings between the lobe and the plasma sheet boundary layer (PSBL) which exhibited the signatures predicted by the theoretical analysis of the generation of broadband electrostatic noise (BEN) by ion beam instabilities. These signatures are a gradual rise in the upper frequency of BEN as the spacecraft approaches the plasma boundary layer, and a very rapid rise in the upper frequency near the crossing into the PSBL from the lobe. Several examples of crossings are presented that exhibit both signatures, as well as a case of crossings in which the gradual frequency rise signature is absent but the rapid rise is present. This case exhibits a BEN in the range expected for the low-frequency ion-ion two-stream and the high-frequency Buneman instability.

Grabbe, Crockett

1989-12-01

33

The prediction of STOVL noise - Current semiempirical methods and comparisons with jet noise data  

Microsoft Academic Search

The prediction of conventional or STOVL turbojet propulsion system-using aircraft noise is presently undertaken by means of a method incorporating empirical models for jet-mixing noise, engine core noise, and broadband shock noise. The free-jet noise is coupled with a novel empirical equation for ground-interaction noise generated by a vertically impinging jet, and supplemented with the out-of-ground-effect free-jet acoustic directivity pattern

Paul T. Soderman

1990-01-01

34

Fan Noise Prediction Assessment.  

National Technical Information Service (NTIS)

This report is an evaluation of two techniques for predicting the fan noise radiation from engine nacelles. The first is a relatively computational intensive finite element technique. The code is named ARC, an abbreviation of Acoustic Radiation Code, and ...

P. H. Bent

1995-01-01

35

Model rotor low frequency broadband noise at moderate tip speeds  

NASA Astrophysics Data System (ADS)

The results of an experimental investigation of low frequency broadband noise (LFBN) radiated from model helicopter rotors are presented. The results are for a range of tip Mach numbers (Mt) up to 0.50. The effect of rotor blade loading, advance ratio, tip speed, number of blades and free stream turbulence on the sound pressure level (SPL) and the spectrum of LFBN have been investigated. The peak SPL of LFBN appears to follow an M(4) law if the effect of rms turbulence velocity is removed. The peak SPL of LFBN seems to saturate with increases in advance ratio and with blade loading, and is proportional to the square of the turbulence integral scale when the effect of rms turbulence velocity and Mt are removed. Also, a simple peak SPL scaling law for noise from a helicopter rotor in forward flight due to convected sinusoidal gust is developed. The trend predicted by this scaling law is found to be satisfactory for the variation of the peak SPL of LFBN with tip speed.

Humbad, N. G.; Harris, W. L.

1980-06-01

36

Fan noise prediction assessment  

Microsoft Academic Search

This report is an evaluation of two techniques for predicting the fan noise radiation from engine nacelles. The first is a relatively computational intensive finite element technique. The code is named ARC, an abbreviation of Acoustic Radiation Code, and was developed by Eversman. This is actually a suite of software that first generates a grid around the nacelle, then solves

Paul H. Bent

1995-01-01

37

Airframe Noise Prediction Method.  

National Technical Information Service (NTIS)

A noise component method is presented for calculating airframe noise. Noise from clean wing and tail surface is represented as trailing edge noise caused by the turbulent boundary layer. Landing gear noise is given by an empirical representation of model ...

M. R. Fink

1977-01-01

38

Fan noise prediction assessment  

NASA Astrophysics Data System (ADS)

This report is an evaluation of two techniques for predicting the fan noise radiation from engine nacelles. The first is a relatively computational intensive finite element technique. The code is named ARC, an abbreviation of Acoustic Radiation Code, and was developed by Eversman. This is actually a suite of software that first generates a grid around the nacelle, then solves for the potential flowfield, and finally solves the acoustic radiation problem. The second approach is an analytical technique requiring minimal computational effort. This is termed the cutoff ratio technique and was developed by Rice. Details of the duct geometry, such as the hub-to-tip ratio and Mach number of the flow in the duct, and modal content of the duct noise are required for proper prediction.

Bent, Paul H.

1995-05-01

39

Generation of broadband noise in the magnetotail  

NASA Astrophysics Data System (ADS)

The generation of electrostatic noise in the geomagnetic tail by ion beams is evaluated. A stationary plasma-sheet electron distribution and streaming ion distributions is assumed. Both warm ion streams, as observed within the plasma sheet boundary layer, and cold ion streams, as expected from upward flowing ionospheric ions, are considered. Warm ion streams by themselves are found to be stable, whereas a cold ion stream by itself is unstable to the beam acoustic model. However, wave growth is increased if both cold and warm streams are simultaneously present. These results suggest that the interaction between the warm and cold ion streams is responsible for the peak in electrostatic wave intensities observed within the plasma sheet boundary layer. For cold and warm ions streaming in the same direction, we find wave growth peaks for wave normal angles theta = O deg and wave frequencies about 0.1 x the electron plasma frequency. However, for anti-parallel streaming cold and warm ions, wave growth peaks near theta approx = 90 deg and wave frequencies are an order of magnitude smaller. Including counter streaming warm ions in addition to a cold ion stream in wave growth that is a superposition of that for the above two cases.

Dusenbery, P. B.; Lyons, Lawrence R.

1987-03-01

40

Noise predictive turbo systems  

Microsoft Academic Search

Iterative decoding has been widely studied for memoryless white Gaussian noise channels. For nonideal channels, e.g., correlated noise channels, iterative decoding combined with iterative noise estimation may improve the performance of the detector. The basic idea is to exploit the decoding results of the previous iteration to estimate the correlated noise so that better decoding results ran be obtained. Furthermore,

Yunxiang Wu; J. R. Cruz

2001-01-01

41

Acoustic Environment of Admiralty Inlet: Broadband Noise Measurements  

SciTech Connect

Admiralty Inlet has been selected as a potential tidal energy site. It is located near shipping lanes, is a highly variable acoustic environment, and is frequented by the highly endangered southern resident killer whale (SRKW). Resolving environmental impacts is the first step to receiving approval to deploy tidal turbines at Admiralty Inlet. Of particular concern is the potential for blade strike or other negative interactions between the SRKW and the tidal turbine. A variety of technologies including passive and active monitoring systems are being considered as potential tools to determine the presence of SRKW in the vicinity of the turbines. Broadband noise level measurements are critical for the determination of design and operation specifications of all marine and hydrokinetic energy capture technologies. Acoustic environment data at the proposed site was acquired at different depths using a cabled vertical line array (VLA) with four calibrated hydrophones. The sound pressure level (SPL) power spectrum density was estimated based on the fast Fourier transform. This study describes the first broadband SPL measurements for this site at different depths with frequency ranging from 10 kHz to 480 kHz in combination with other information. To understand the SPL caused by this bedload transport, three different pressure sensors with temperature and conductivity were also assembled on the VLA to measure the conditions at the hydrophone deployment depth. The broadband SPL levels at frequency ranges of 3 kHz to 7 kHz as a function of depth were estimated. Only the hydrophone at an average depth of 40 m showed the strong dependence of SPL with distance from the bottom, which was possibly caused by the cobbles shifting on the seabed. Automatic Identification System data were also studied to understand the SPL measurements.

Xu, Jinshan; Deng, Zhiqun; Martinez, Jayson J.; Carlson, Thomas J.; Myers, Joshua R.; Weiland, Mark A.; Jones, Mark E.

2011-09-30

42

Noise prediction technology for CTOL aircraft  

Microsoft Academic Search

The application of a new aircraft noise prediction program to CTOL noise prediction is outlined. Noise prediction is based on semiempirical methods for each of the propulsive system noise sources, such as the fan, the combustor, the turbine, and jet mixing, with noise-critical parameter values derived from the thermodynamic cycle of the engine. Comparisons of measured and predicted noise levels

J. P. Raney

1978-01-01

43

Computation of rotor wake turbulence noise  

Microsoft Academic Search

A major source of fan broadband noise is the interaction of rotor wake turbulence with the fan outlet guide vanes. A broadband noise model that utilizes computed rotor flow turbulence from a Reynolds averaged Navier–Stokes code is used to predict fan broadband noise spectra. The noise model is employed to examine the broadband noise characteristics of the 22-in source diagnostic

M. Nallasamy; E. Envia

2005-01-01

44

Dutch railway noise prediction schemes  

NASA Astrophysics Data System (ADS)

A calculation scheme for the prediction of noise levels along railway lines was completed in 1984 and has been applied since then in the framework of the Dutch Noise Pollution Act. The scheme makes it possible to calculate the equivalent sound levels LAeq at receiver positions up to distances of 1500 m and can be used in almost every situation except large railway yards and large stations. A simplified calculation method working in dB(A) was derived for situations without any screening by obstacles such as barriers. The source model is based on investigations of wheel/rail noise. The source strength and the factors that influence the emission were derived from measurements. The propagation of railway noise over large distances can be predicted by the propagation model that has been used for road traffic noise and industrial noise. The models differ only for the propagation in the region near the source.

van Ruiten, C. J. M.

1988-01-01

45

The prediction of STOVL noise - Current semiempirical methods and comparisons with jet noise data  

NASA Astrophysics Data System (ADS)

The prediction of conventional or STOVL turbojet propulsion system-using aircraft noise is presently undertaken by means of a method incorporating empirical models for jet-mixing noise, engine core noise, and broadband shock noise. The free-jet noise is coupled with a novel empirical equation for ground-interaction noise generated by a vertically impinging jet, and supplemented with the out-of-ground-effect free-jet acoustic directivity pattern of a Harrier-type vectoring nozzle installation. This acoustic-prediction method yielded reasonable agreement with measured far-field Harrier noise during hover in and out of ground effect. Unlike small-scale studies of jet impingement on a hard surface, no tones were found in the present Harrier nozzle spectra.

Soderman, Paul T.

1990-04-01

46

Fan Noise Source Diagnostic Test Computation of Rotor Wake Turbulence Noise  

Microsoft Academic Search

An important source mechanism of fan broadband noise is the interaction of rotor wake turbulence with the fan outlet guide vanes. A broadband noise model that utilizes computed rotor flow turbulence from a RANS code is used to predict fan broadband noise spectra. The noise model is employed to examine the broadband noise characteristics of the 22-inch Source Diagnostic Test

M. Nallasamy; E. Envia; S. A. Thorp; A. Shabbir

2002-01-01

47

Semi-Empirical Modelling of Broadband Noise for Aerofoils  

NASA Astrophysics Data System (ADS)

Turbulence related noise is widely recognized to be one of the most important aerodynamic noise sources for many applications and the development of computational tools for its modelling and prediction is an even more important target in many areas of applied engineering. On a general basis the noise generation mechanisms that can occur on an aerofoil surface can be classified in three main categories: Turbulent Boundary Layer-Trailing Edge noise (TBL-TE), the Laminar Boundary Layer--Vortex Shedding (LBL-VS) noise and the Separation Stall (S-S) noise, respectively related to the boundary layer turbulent eddies, to the boundary layer laminar instabilities and to the large vorticity that can be experienced for different Angle of Attacks, Reynolds and Mach numbers. Despite of the recent improvements of Computational Fluid Dynamics in the frame of turbulence modelling, the numerical computation of high Reynolds flow field turbulence for acoustic purposes is still a hard task to perform as it requires a time-dependant, fully-resolved Large Eddy Simulation often resulting in a prohibitive computational cost. Furthermore in most of the cases it is of fundamental importance to have fast and reliable tools able to capture the driving phenomena and noise sources, in order to be able to perform a large number of simulations embedded in an optimization cycle. The target of this paper is testing the Brooks, Pope and Marcolini semi-empirical model for noise prediction of the NACA 0012 aerofoil on the DU96 geometry in a range of Angle of Attacks from 3 to 10 degrees and Reynolds numbers from 1.5 to 3.1 M. The semi-empirical model input parameters (boundary layer, displacement and momentum thickness) on the suction and pressure side of the aerofoil at the trailing edge location are computed with a steady RANS simulation while the BPM approach has been implemented as an external tool. Computed noise spectra show a good agreement with experimental data from literature in terms of both Sound Pressure Levels (SPLs) and spectra envelope.

de Gennaro, Michele; Kuehnelt, Helmut

2011-09-01

48

Geoacoustic inversion using broadband noise from surface ships  

NASA Astrophysics Data System (ADS)

Spatiotemporal techniques developed for geoacoustic inversion using broadband noise from surface ships will be discussed. Inversion processing will be demonstrated with data obtained from a bottom-mounted horizontal line array at a depth of 110 m in the Gulf of Mexico near Corpus Christi, TX. The inversion solutions for the geoacoustic solutions are validated by comparing modeled transmission loss at several frequencies with loss from a towed source that was measured in another portion of the experiment. The first step in developing the inversion algorithm was to obtain consistent results for geoacoustic parameters when the source track reconstruction is available. That such robustness requires temporal samples in the cost function is established from the results of inversions from normalized cross spectra. The next step in the algorithm development was to perform simultaneous inversion for geoacoustic and uniform source motion parameters to examine complications that might arise when source track reconstruction is unavailable. Examples showing the effect on robustness due to violations of uniform motion are presented. Also, the advantages and applications of alternative cost functions that match the structure in received level data and modeled fields will be described. [Work supported by ONR.

Koch, Robert A.; Knobles, D. P.

2005-09-01

49

Comparisons of Surface and Borehole Broadband Ambient Seismic Noise at IRIS Station RAR: Raratonga, Cook Islands.  

National Technical Information Service (NTIS)

This report addresses reduction of ambient broadband (.01 - 10 Hz) seismic noise achieved by a 100 m deep borehole deployment on a small oceanic island, Raratonga in the Cook Islands, relative to simultaneously recorded surface levels. Between .5 - 5 Hz, ...

H. K. Given

1992-01-01

50

Broadband noise characteristics of a model counter-rotating shrouded propfan  

NASA Astrophysics Data System (ADS)

In recent years counter-rotating propfan aeroengines were developed since they promise significant fuel savings compared to conventional fan engines. The German manufacturer MTU has developed the CRISP (Counter-Rotating Integrated Shrouded Propfan) 1:6.25-scale model engine which has been tested in the German Dutch Wind Tunnel (DNW). The present study concentrates on the broadband noise component and its relative importance to the total sound emission. While single-propeller/propfan noise emission is dominated by rotational noise, a counter-rotating propfan may constitute a significant source of broadband noise.

Boettcher, Jan; Dobrzynski, Werner; Gehlhar, Burkhard

51

Fan Noise Prediction with Applications to Aircraft System Noise Assessment.  

National Technical Information Service (NTIS)

This paper describes an assessment of current fan noise prediction tools by comparing measured and predicted sideline acoustic levels from a benchmark fan noise wind tunnel test. Specifically, an empirical method and newly developed coupled computational ...

C. L. Burley D. M. Nark E. Envia

2009-01-01

52

Emergence of broadband Rayleigh waves from correlations of the ambient seismic noise  

Microsoft Academic Search

We demonstrate that the coherent information about the Earth structure can be extracted from the ambient seismic noise. We compute cross-correlations of vertical component records of several days of seismic noise at different pairs of stations separated by distances from about one hundred to more than two thousand kilometers. Coherent broadband dispersive wavetrains clearly emerge with group velocities similar to

N. M. Shapiro; M. Campillo

2004-01-01

53

Broad-band noise spectroscopy of giant magnetoresistive read heads  

Microsoft Academic Search

This paper describes wide-band (1 MHz-10 GHz) thermal magnetic fluctuation (TMF) noise measurements conducted on magnetoresistive devices such as giant magnetoresistive (GMR) and tunnel junction magnetoresistive (TMR) heads. The paper discusses the instrumentation, as well as the corrections necessary to separate the TMF noise from the total noise as collected. It shows that the thermal electrical noise component of this

Klaas B. Klaassen; Xinzhi Xing; Jack C. L. van Peppen

2005-01-01

54

Discrete-frequency and broadband noise radiation from diesel engine cooling fans  

NASA Astrophysics Data System (ADS)

This effort focuses on measuring and predicting the discrete-frequency and broadband noise radiated by diesel engine cooling fans. Unsteady forces developed by the interaction of the fan blade with inlet flow are the dominant source for both discrete-frequency and broadband noise of the subject propeller fan. In many cases, a primary source of discrepancy between fan noise prediction and measurement is due to incomplete description of the fan inflow. Particularly, in such engine cooling systems where space is very limited, it would be very difficult, if not, impossible to measure the fan inflow velocity field using the conventional, stationary hot-wire method. Instead, the fan inflow was measured with two-component x-type hot-film probes attached very close to the leading edge of a rotating blade. One of the advantages of the blade-mounted-probe measurement technique is that it measures velocities relative to the rotating probe, which enables the acquired data to be applied directly in many aerodynamic theories that have been developed for the airfoil fixed-coordinate system. However, the velocity time data measured by this technique contains the spatially non-uniform mean velocity field along with the temporal fluctuations. A phase-locked averaging technique was successfully employed to decompose the velocity data into time-invariant flow distortions and fluctuations due to turbulence. The angles of attack of the fan blades, obtained from inlet flow measurements, indicate that the blades are stalled. The fan's radiated noise was measured without contamination from the engine noise by driving the fan with an electric motor. The motor operated at a constant speed while a pair of speed controllable pulleys controlled the fan speed. Narrowband and 1/3-octave band sound power of the cooling fan was measured by using the comparison method with a reference sound source in a reverberant room. The spatially non-uniform mean velocity field was used in axial-flow fan noise theory to predict the discrete-frequency noise at the blade passing frequency (BPF) and harmonics. The unsteady lift was predicted by considering transverse and longitudinal velocity fluctuations. The influences due to an upstream finger guard were also investigated. The radiated sound power spectra that were measured for the fan are shown to be in excellent agreement with those predicted. The agreement between prediction and measurement is only fair at the fundamental BPF tone. Further experimental investigations revealed that the interaction noise between the fan blades and a shroud surrounding the fan might be the dominant source for the radiation at the first harmonic. The space-time correlation functions of the inflow velocity fluctuations were measured and utilized in stochastic lifting surface theory to calculate the unsteady blade lift and resulting broadband fan noise. The integral length scale of the inlet flow was found to be much smaller than the blade-to-blade separate distance of the fan. Therefore, contributions from blade-to-blade correlations of the various elements on different blades were found to be negligible and hence ignored; only the correlations between the strip elements on a given blade were considered. The cross-correlations measured between elements separated by more than the integral length scale were also found to be negligibly small. The predicted broadband sound power spectra agree well with those measured for frequencies greater than 400 Hz. There are deviations between the predictions and measurements at lower frequencies. These are likely due to fan blade stall, and possibly, anomalies in the noise measurement environment. In order to reduce the sound radiation at the blade rate tones, the baseline fan was replaced with a skewed fan. The backward skew angle of 30° was found to effectively reduce the 2nd and higher harmonics of the blade rate tone. The interaction of the shroud opening and the blade tips dominates the sound level at the fundamental tone. This tone was successfully reduced by incorporating a serrated shroud ope

Kim, Geon-Seok

55

Electronics Cooling Fan Noise Prediction  

Microsoft Academic Search

Using the finite volume CFD software FLUENT, one fan was studied at a given flow rate (1.5m3\\/min) for three different operational rotating speeds : 2,000, 2,350 and 2,700 rpm. The turbulent air flow analysis predicts the acoustic behavior of the fan. The best fan operating window, i.e. the one giving the best ratio between noise emissions and cooling performance, can

Antoine Dozolme; Hossam Metwally; Thierry Marchal

2007-01-01

56

Fan Noise Prediction: Status and Needs.  

National Technical Information Service (NTIS)

The prediction of fan noise is an important part to the prediction of overall turbofan engine noise. Advances in computers and better understanding of the flow physics have allowed researchers to compute sound generation from first principles and rely les...

D. L. Huff

1997-01-01

57

Interim Prediction Method for Turbine Noise.  

National Technical Information Service (NTIS)

A turbine noise prediction method for interim use in the NASA Aircraft Noise Prediction Program is selected. The method predicts the level, directivity, and one-third octave band spectra of far field turbine noise as a function of engine parameters. The s...

E. A. Krejsa M. F. Valerino

1976-01-01

58

NASA progress in aircraft noise prediction  

Microsoft Academic Search

Langley Research Center efforts to develop a methodology for predicting the effective perceived noise level (EPNL) produced by jet-powered CTOL aircraft to an accuracy of + or - 1.5 dB are summarized with emphasis on the aircraft noise prediction program (ANOPP) which contains a complete set of prediction methods for CTOL aircraft including propulsion system noise sources, aerodynamic or airframe

J. P. Raney; S. L. Padula; W. E. Zorumski

1981-01-01

59

Handoff Prediction by Mobility Characteristics in Wireless Broadband Networks  

Microsoft Academic Search

The paper proposes mobility-aided resource reservation (MARR) with admission control (AC) to provide better usage of scarce resources in wireless broadband networks. The area of a cell is divided into an outer ring and an inner ring. A target cell is predicted by extrapolating the trajectory of each MS. In order to reduce signaling overhead, bandwidth is reserved only in

Li-liann Lu; Jean-lien C. Wu

2005-01-01

60

Prediction level of noise by a helicopter  

NASA Astrophysics Data System (ADS)

This paper describes the prediction level of noise which is generated by a helicopter. The relation between noise levels and distance from the helicopter to an observing point is measured. From these measured results, acoustic power level generated by the helicopter is calculated. Noise levels can be estimated by measuring the distance from the helicopter's flight path. Prediction of the noise levels is in good agreement with measured noise levels.

Shibayama, Hideo; Takayama, Takashi; Nakamura, Shin'iti

61

Some analytic results for the study of broadband noise radiation from wings, propellers and jets in uniform motion  

Microsoft Academic Search

Alan Powell has made significant contributions to t he understanding of many aeroacoustic problems, in particular, the problems of broadband noise from jets and boundary layers. In this paper, some analytic resu lts are presented for the calculation of the correlation function of the broadband noise rad iated from a wing, a propeller, and a jet in uniform forward motion.

F. Farassat; J. Casper

2003-01-01

62

The Broad-band Noise Characteristics of Selected AXPs and SGRs: Probing the Magnetar Coronae  

NASA Astrophysics Data System (ADS)

We present the broad-band noise structure of Anomalous X-Ray Pulsars (AXPs) and Soft Gamma Repeaters (SGRs) in the 2-60 keV energy band which are thought to be powered by either magnetic decay (Thompson & Duncan 1995) or accretion (Alpar 2001). We have used Rossi X-ray Timing Explorer (R-XTE) PCA archival light curves and derived time series for 4 AXPs and 1 SGR. We detect that AXP and SGR sources show band limited noise at low frequencies in the range 0.005-0.05 Hz. We find that this noise level can be associated with their bursts, glitches or flaring activities. We discover band-limited red noise in 1E 2259+586 only for about two years after its outburst and the associated glitch. The system shows no broad-band noise otherwise. The other three AXPs indicate a lower band-limited noise level in comparison with 1E 2259+586 and it is persistent, but show variations. We favour a model where this broad-band noise particularly as detected in 1E 2259+586 is related to the Compton scattering of thermal photons in the magnetar corona and thus reveal coronal time scales and activity.

Külebi, Baybars; Balman, ?ölen

2008-02-01

63

Toward a Sub-Decibel Noise Figure Broadband Monolithic LNA in Silicon  

Microsoft Academic Search

This paper reports a first attempt toward realization of a single-chip silicon-based broadband (BW-3dB > 5 GHz) low-noise amplifier (LNA) with a noise figure (NF) of less than 1 dB across the band. A differential common-emitter amplifier with active feedback and neutralization capacitance is adopted without using passives at the input that consume chip area and deteriorate NF due to

Ankush Goel; Hossein Hashemi

2008-01-01

64

Spectral Characteristics of Noise in Broadband Stations of Kandilli Observatory and Earthquake Research Institue  

Microsoft Academic Search

In this study, the seismic noise levels of the Broadband Stations operated by Bogazici University Kandilli Observatory and Earthquake Research Institue, in Turkey are investigated for periods ranging from 0.01 to 100 sec. The data are selected to reflect different conditions including seasonal and daily variations. The method which was applied consisted of first removing the instrument response to obtain

A. Koseoglu Kusmezer; M. Aktar

2008-01-01

65

Broadband maximum likelihood estimation of shallow ocean parameters using shipping noise  

Microsoft Academic Search

Environmental parameter estimation for a shallow ocean is addressed by using wideband shipping noise as a source of acoustic energy. Unknown locations of the broadband acoustic sources are estimated simultaneously with the ocean depth using the approximate conditional maximum likelihood estimator (CMLE). This procedure is tested via computer simulations and applied to the experimental hydrophone towed array data

C. F. Mecklenbrauker; A. Gershman

2001-01-01

66

Noise-predictive maximum likelihood (NPML) detection  

Microsoft Academic Search

Sequence detectors for the digital magnetic recording channel that are based on noise-predictive partial-response equalization are described. Called Noise-Predictive Maximum Likelihood (NPML) detectors, they arise by imbedding a noise prediction\\/whitening process into the branch metric computation of a Viterbi detector. NPML detectors can be realized in a form that allows RAM table look-up implementation of the imbedded feedback. Alternatively, the

J. D. Coker; Evangelos Eleftheriou; Richard L. Galbraith; Walter Hirt

1998-01-01

67

Rotor noise prediction technology: Theoretical approach  

Microsoft Academic Search

Helicopter rotors which are the most complicated noise generators among rotating blade machinery are discussed. The main or the tail rotor can be the dominant source of noise depending on the range of frequencies and the observer position. Significant advances in noise prediction were made. Acoustic analysis is the most successful and general theoretical method to treat the acoustics of

F. Farassat

1982-01-01

68

Numerical Prediction of Laminar Instability Noise for NACA 0012 Aerofoil  

NASA Astrophysics Data System (ADS)

Aerofoil self-generated noise is recognized to be of fundamental importance in the frame of applied aeroacoustics and the use of computational methods to assess the acoustic behaviour of airframe components challenges an even larger community of engineers and scientists. Several noise generation mechanisms can be found which are mainly related to the physical development of turbulence over the boundary layer. They can be classified in 3 main categories: the Turbulent Boundary Layer--Trailing Edge noise (TBL-TE), the Laminar Boundary Layer--Vortex Shedding (LBL-VS) noise and the Separation Stall (S-S) noise. The TBL-TE is mainly related to the noise generated by turbulent eddies which develop into the boundary layer and usually exhibits a broadband spectrum. The LBL-VS is related to laminar instabilities that can occur within the boundary layer which are responsible for a very late transition and generate a typical peaked tonal noise, while the S-S noise mainly results from the development of large vortices after the separation point. In this paper we propose a numerical analysis targeted to the simulation the LBL-VS noise mechanisms on a NACA 0012 aerofoil, tested at a Reynolds number of 1.1 M and Mach number of 0.2. The aerodynamic simulation is performed with a 2D transient RANS approach using the k-? transitional turbulence model, while the acoustic computations are performed with the FfowcsWilliams-Hawkings (FW-H) acoustic analogy and with a Finite Element (FE) approach solving Lighthill's wave equation. Computed noise spectra are compared with experimental data published by NASA showing a good agreement both for peak location as well as for the predicted noise level.

de Gennaro, Michele; Hueppe, Andreas; Kuehnelt, Helmut; Kaltenbacher, Manfred

2011-09-01

69

Design of SiGe HBT UWB low noise amplifier employing broadband noise canceling  

Microsoft Academic Search

A SiGe HBT low-noise amplifier (LNA) for UWB application is presented. According to the analysis for noise of common base transistor, noise canceling structure for SiGe HBT is proposed to reduce the noise arising from common transistor, thus reduce the noise of LNA. Meanwhile it also compensate the gain of the LNA, thus improves the gain flatness. The chip layout

Chunbao Ding; Wanrong Zhang; Hongyun Xie; Liang Chen; Pei Shen; Donghui Zhang; Boyu Liu; Yongqiang Zhou; Zhengjie Guo; Zhiyi Lu

2011-01-01

70

Interim Prediction Method for Jet Noise.  

National Technical Information Service (NTIS)

A method is provided for predicting jet noise for a wide range of nozzle geometries and operating conditions of interest for aircraft engines. Jet noise theory, data and existing prediction methods was reviewed, and based on this information a interim met...

J. R. Stone

1974-01-01

71

Assessment of NASA's Aircraft Noise Prediction Capability.  

National Technical Information Service (NTIS)

A goal of NASA s Fundamental Aeronautics Program is the improvement of aircraft noise prediction. This document provides an assessment, conducted from 2006 to 2009, on the current state of the art for aircraft noise prediction by carefully analyzing the r...

M. D. Dahl

2012-01-01

72

Broadband noise characteristics of a model counter-rotating shrouded propfan  

Microsoft Academic Search

In recent years counter-rotating propfan aeroengines were developed since they promise significant fuel savings compared to conventional fan engines. The German manufacturer MTU has developed the CRISP (Counter-Rotating Integrated Shrouded Propfan) 1:6.25-scale model engine which has been tested in the German Dutch Wind Tunnel (DNW). The present study concentrates on the broadband noise component and its relative importance to the

Jan Boettcher; Werner Dobrzynski; Burkhard Gehlhar

1992-01-01

73

On the detection and classification of quadrature digital modulations in broad-band noise  

Microsoft Academic Search

Optimal and suboptimal decision rules for the detection of constant-envelope quadrature digital modulations in broadband noise are derived and analyzed. The effect of various stochastic models for the carrier phase is examined in detail, while no epoch or frequency uncertainty is assumed. The delay-and-multiply type of detector is considered. A new binary\\/quadrature phase shift keying (BPSK\\/QPSK) classifier is compared to

A. Polydoros; K. Kim

1990-01-01

74

Aircraft noise prediction program theoretical manual, part 2  

Microsoft Academic Search

Detailed prediction methods for specific aircraft noise sources are given. These sources are airframe noise, combustion noise, fan noise, single and dual stream jet noise, and turbine noise. Modifications to the NASA methods which comply with the International Civil Aviation Organization standard method for aircraft noise prediction are given.

W. E. Zorumski

1982-01-01

75

The broad-band noise characteristics of selected anomalous X-ray pulsars and soft gamma-ray repeaters  

NASA Astrophysics Data System (ADS)

We present the broad-band noise structure of selected anomalous X-ray pulsars (AXPs) and soft gamma-ray repeaters (SGRs) in the 2-60keV energy band. We have analysed Rossi X-Ray Timing Explorer Proportional Counter Array archival light curves for four AXPs and one SGR. We detect that the persistent emission of these sources shows band-limited noise at low frequencies in the range 0.005-0.05Hz varying from 2.5 to 70 per cent integrated rms in times of prolonged quiescence and following outbursts. We discovered band-limited red noise in 1E2259+586 only for ~2yr after its major 2002 outburst. The system shows no broad-band noise otherwise. Although this rise in noise in 1E2259+586 occurred following an outburst which included a rotational glitch, the other glitching AXPs showed no obvious change in broad-band noise, thus it does not seem that this noise is correlated with glitches. The only source that showed significant variation in broad-band noise was 1E1048.1-5937, where the noise gradually rose for 1.95yr at a rate of ~3.6 per cent per year. For this source the increases in broad-band noise was not correlated with the large increases in persistent and pulsed flux, or its two short SGR-like bursts. This rise in noise did commence after a long burst, however, given the sparsity of this event, and the possibility that similar bursts went unnoticed the trigger for the rise is noise in 1E1048.1-5937 is not as clear as for 1E2259+586. The other three sources indicate a persistent band-limited noise at low levels in comparison.

Külebi, B.; Balman, ?.

2009-06-01

76

Wind turbine noise: Prediction tools and design parameter dependence  

NASA Astrophysics Data System (ADS)

Wind turbine aerodynamic noise sources are described, and noise predictions and measurements are compared. The influence of design parameters and variable running speed on noise emission is discussed. Results show that prediction tools for blade tower passage noise predict noise emission reasonably well. Prediction tools for high frequency noise are not sufficient. Reliable noise measurements for different machines are needed. It is important to take background noise levels into account when noise criteria are decided. Noise emission is highly dependent on rotational speed and running a turbine with variable rpm lowers noise emission for low wind speeds.

Meijer, S.

1984-11-01

77

Internal Noise Prediction within Aircraft Cabin.  

National Technical Information Service (NTIS)

For about two decades, Structural Dynamics and Coupled Systems Department of ONERA has developed, validated and applied different methods for modeling and predicting internal and external noise of complex structures in the low (LF), medium (MF) and high (...

J. David

2004-01-01

78

Aerodynamic noise prediction using grey model  

Microsoft Academic Search

In this paper, two methods are described to predict the aerodynamic noise induced by flow around a cylinder using the linear model GM (1, 1) and the nonlinear model Verhult based on grey system theory. The grey prediction initial data is from large eddy simulation and acoustic analogy. The prediction results using the model GM(1, 1) are respectively compared to

Long Shuangli; Nie Hong; Li Lei; Xu Xin

2010-01-01

79

Validation of the Lower Tagus Valley velocity and structural model using ambient noise broadband measurements  

NASA Astrophysics Data System (ADS)

Along his history the Lower Tagus Valley (LTV) region was shaken by several earthquakes, some of them were produced in large ruptures of offshore structures located southwest of the Portuguese coastline, among these we the Lisbon earthquake of 1 November 1755; other moderates earthquakes were produced by local sources such as the 1344, 1531 and the 1909 Benavente earthquake. In order to promote an improved assessment of the seismic hazard in this region, we propose the introduction of realistic methods on the prediction of ground motion produced by moderate to large earthquakes in LTV. This process involves the establishment of a structural 3D model based on all the available geophysical and geotechnical data on the area (seismic, gravimetric, deep wells and geological outcrops) and the determination of wave propagation from a finite difference method: by applying the E3D program [1,2]. To confirm this model we use broadband ambient noise measurements collected in two profiles with azimuth perpendicular to the basin axis and we applied the horizontal to vertical (H/V) spectral ratio method [3] to the recordings in order to estimate the amplification of the basin. The H/V curves obtained reveals the existence of two low frequency peaks centered on 0.2 a 1 Hz frequencies[4]. These peaks are strongly related with the thickness of Cenozoic and alluvial sediments. By inversion of the H/V curve, we obtain a more detailed velocity model for the region where the profile were determined, which is in good agreement with borehole data and other results obtained with magnetic and seismic reflection methods.

Torres, R. J. G.; Furtado, J. A.; Silva, H. G.; Borges, J. F.; Caldeira, B.; Bezzeghoud, M.; Cancela Pinto, C.; Carvalho, J.

2012-04-01

80

Numerical prediction of wind turbine noise  

Microsoft Academic Search

This paper develops and validates the first principle based numerical method for predicting the noise radiated from the rotating Horizontal-Axis Wind Turbine (HAWT) blades. The noise radiated to the far-field was predicted by the code based on Ffowcs Williams–Hawkings (FW–H) equation, using both original non-permeable formulation and permeable formulation. A commercially available CFD solver, ANSYS CFX 11.0, was used to

A. Tadamasa; M. Zangeneh

2011-01-01

81

Investigation of a broadband duct noise control system inspired by the middle ear mechanism  

NASA Astrophysics Data System (ADS)

A new duct noise control device is introduced based on the mechanism of human middle ear which functions as a compact, broadband impedance transformer between the air motion in the outer ear and the liquid motion in the inner ear. The system consists of two rigid endplates, simulating the tympanic membrane and the stapes footplate, and they are connected by a single rigid rod, simulating the overall action of the ossicular chain. These three pieces are placed in a side-branch cavity, and the whole device is called an ossicular silencer. A specific configuration is investigated numerically with a two-dimensional finite element model. Results show that broadband noise attenuation can be achieved in the very low frequency regime. Typically, two or more resonance peaks are found and the transmission loss between two neighbouring peaks is maintained at a high level. The cavity length is found to be the most crucial parameter that determines the effective frequency range of the ossicular silencer. The total cavity volume, which is a major controlling factor in most existing noise control devices, becomes less influential. The fluid medium in the enclosed cavity mainly acts like an added mass, while its stiffness effect is negligible. Simplified plane wave analysis is also conducted to reveal the mechanisms of the system resonances. The first resonance is identified as of the mass-spring system with mass contributions from both fluid and the plates, while the second one is of the Herschel-Quincke (HQ) tube resonance.

Wang, Chunqi; Huang, Lixi

2012-08-01

82

Decoherence times of universal two-qubit gates in the presence of broad-band noise  

NASA Astrophysics Data System (ADS)

The controlled generation of entangled states of two quantum bits is a fundamental step toward the implementation of a quantum information processor. In nano-devices this operation is counteracted by the solid-state environment, characterized by a broadband and non-monotonic power spectrum, often 1/f, at low frequencies. For single-qubit gates, incoherent processes due to fluctuations acting on different time scales result in peculiar short- and long-time behavior. Markovian noise gives rise to exponential decay with relaxation and decoherence times, T1 and T2, simply related to the symmetry of the qubit-environment coupling Hamiltonian. Noise with the 1/f power spectrum at low frequencies is instead responsible for defocusing processes and algebraic short-time behavior. In this paper, we identify the relevant decoherence times of an entangling operation due to the different decoherence channels originating from solid-state noise. Entanglement is quantified by concurrence, which we evaluate in an analytic form employing a multi-stage approach. The ‘optimal’ operating conditions of reduced sensitivity to noise sources are identified. We apply this analysis to a superconducting \\sqrt { {i}-SWAP} gate for experimental noise spectra.

Paladino, E.; D'Arrigo, A.; Mastellone, A.; Falci, G.

2011-09-01

83

Validation of helicopter noise prediction techniques  

NASA Astrophysics Data System (ADS)

The current techniques of helicopter rotor noise prediction attempt to describe the details of the noise field precisely and remove the empiricisms and restrictions inherent in previous methods. These techniques require detailed inputs of the rotor geometry, operating conditions, and blade surface pressure distribution. The purpose of this paper is to review those techniques in general and the Farassat/Nystrom analysis in particular. The predictions of the Farassat/Nystrom noise computer program, using both measured and calculated blade surface pressure data, are compared to measured noise level data. This study is based on a contract from NASA to Bolt Beranek and Newman Inc. with measured data from the AH-1G Helicopter Operational Loads Survey flight test program supplied by Bell Helicopter Textron.

Succi, G. P.

1981-04-01

84

Flow and noise predictions for the tandem cylinder aeroacoustic benchmark  

NASA Astrophysics Data System (ADS)

Flow and noise predictions for the tandem cylinder benchmark are performed using lattice Boltzmann and Ffowcs Williams-Hawkings methods. The numerical results are compared to experimental measurements from the Basic Aerodynamic Research Tunnel and Quiet Flow Facility (QFF) at NASA Langley Research Center. The present study focuses on two configurations: the first configuration corresponds to the typical setup with uniform inflow and spanwise periodic boundary condition. To investigate installation effects, the second configuration matches the QFF setup and geometry, including the rectangular open jet nozzle, and the two vertical side plates mounted in the span to support the test models. For both simulations, the full span of 16 cylinder diameters is simulated, matching the experimental dimensions. Overall, good agreement is obtained with the experimental surface data, flow field, and radiated noise measurements. In particular, the presence of the side plates significantly reduces the excessive spanwise coherence observed with periodic boundary conditions and improves the predictions of the tonal peak amplitude in the far-field noise spectra. Inclusion of the contributions from the side plates in the calculation of the radiated noise shows an overall increase in the predicted spectra and directivity, leading to a better match with the experimental measurements. The measured increase is about 1 to 2 dB at the main shedding frequency and harmonics, and is likely caused by reflections on the spanwise side plates. The broadband levels are also slightly higher by about 2 to 3 dB, likely due to the shear layers from the nozzle exit impacting the side plates.

Brès, Guillaume A.; Freed, David; Wessels, Michael; Noelting, Swen; Pérot, Franck

2012-03-01

85

Noise prediction of a low speed airfoil  

NASA Astrophysics Data System (ADS)

The goal of this work is accurate and efficient prediction of flow generated noise in the presence of solid objects. Flow around a low speed airfoil is considered at chord Reynolds number of Re = 150 000. This flow configuration represents an important aeroacoustics problem with complex physical effects including solid boundaries, boundary layers with pressure gradient, transition and turbulent wake. In the framework of Lighthill's acoustics analogy the procedure of sound prediction is divided into two steps: calculation of sound sources generated by flow and propagation of sound into far field. To calculate flow induced noise sources we performed a high resolution LES as well as a more affordable LES on fewer grid points. Sound propagation and diffraction by the airfoil are accurately are accounted for using numerically computed Green's functions tailored to the airfoil geometry. We will compare the noise spectra using this Green's function with previous calculations using an approximate Green's function.

Khalighi, Yaser; Wang, Meng; Bodony, Daniel; Moin, Parviz

2006-11-01

86

Noise prediction of a low speed airfoil  

Microsoft Academic Search

The goal of this work is accurate and efficient prediction of flow generated noise in the presence of solid objects. Flow around a low speed airfoil is considered at chord Reynolds number of Re = 150 000. This flow configuration represents an important aeroacoustics problem with complex physical effects including solid boundaries, boundary layers with pressure gradient, transition and turbulent

Yaser Khalighi; Meng Wang; Daniel Bodony; Parviz Moin

2006-01-01

87

Prediction of helicopter rotor rotational noise  

Microsoft Academic Search

Based on Farassat (1981) formulation 1A for subsonic time domain, a method is developed for predicting the rotor rotational noise, which is valid for arbitrary observer positions and all linear flight conditions. Without considering the elasticity of the blade, the retarded time equation and all of the integrands in the formulation 1A are derived and expressed as the proper form

Guohua Xu; Zheng Gao

1991-01-01

88

Broadband noise suppression and feature identification of ECG waveforms using mathematical morphology and embedding theorem.  

PubMed

The paper presents an adaptive morphological filter developed using multiscale mathematical morphology (MM) to reject broadband noise from ECG signals without affecting the feature waveforms. As a pre-processing procedure, the adaptive morphological filter cleans an ECG signal to prepare it for further analysis. The noiseless ECG signal is embedded within a two-dimensional phase space to form a binary image and the identification of the feature waveforms is carried out based on the information presented by the image. The classification of the feature waveforms is implemented by an adaptive clustering technique according to the geometric information represented by the image in the phase space. Simulation studies on ECG records from the MIT-BIH and BIDMC databases have demonstrated the effectiveness and accuracy of the proposed methods. PMID:24094825

Ji, T Y; Wu, Q H

2013-09-02

89

Application of virtual sensors in three-dimensional broadband active noise control and the effects on the quiet zones  

Microsoft Academic Search

?This paper presents various experimental results of a real-time, multiple-channel, broadband Active Noise Control (ANC) system, employing the Remote Microphone Technique (RMT) as virtual sensing algorithm in different settings. The effects of virtual sensing on the shape and size of the quiet zone are experimentally investigated. To enhance the quiet zone, an acoustic energy density probe can be used as

Paul S. Booij; Arthur P. Berkhoff

2011-01-01

90

Comparison of Measured and Predicted Airfoil Self-Noise with Application to Wind Turbine Noise Reduction.  

National Technical Information Service (NTIS)

In the ongoing JOULE-III project Development of Design Tools for Reduced Aerodynamic Noise Wind Turbines (DRAW), prediction codes for inflowturbulence (IT) noise and turbulent boundary layer trailing-edge (TE) noise, are developed and validated. It is sho...

T. Dassen S. Wagner R. Parchen S. Kang G. Guidati

1997-01-01

91

A new approach to complete aircraft landing gear noise prediction  

Microsoft Academic Search

This thesis describes a new landing gear noise prediction system developed at The Pennsylvania State University, called Landing Gear Model and Acoustic Prediction code (LGMAP). LGMAP is used to predict the noise of an isolated or installed landing gear geometry. The predictions include several techniques to approximate the aeroacoustic and aerodynamic interactions of landing gear noise generation. These include (1)

Leonard V. Lopes

2009-01-01

92

Numerical noise prediction in fluid machinery  

Microsoft Academic Search

Numerical methods successively became important in the design and optimization of fluid machinery. However, as noise emission\\u000a is considered, one can hardly find standardized prediction methods combining flow and acoustical optimization. Several numerical\\u000a field methods for sound calculations have been developed. Due to the complexity of the considered flow, approaches must be\\u000a chosen to avoid exhaustive computing. In this contribution

Iris Pantle; Franco Magagnato; Martin Gabi

2005-01-01

93

Initial noise predictions for rudimentary landing gear  

NASA Astrophysics Data System (ADS)

A four-wheel "rudimentary" landing gear (RLG) truck was designed for public-domain research, with a level of complexity which is manageable in current numerical simulations, and a weak Reynolds-number sensitivity. Experimental measurements of wall-pressure fluctuations are allowing a meaningful test of unsteady simulations with emphasis on noise generation. We present three Detached-Eddy Simulations (DES) using up to 18 million points in the high-order NTS code. The first is incompressible with the model placed in the wind tunnel, as requested for the 2010 workshop on Benchmark problems for Airframe Noise Computations (BANC-I), intended for force and surface-pressure studies. The second and third are at Mach 0.115 and Mach 0.23, with only one wall, a "ceiling" analogous to a wing (but infinite and inviscid), and are used to exercise far-field noise prediction by coupling the Detached-Eddy Simulations and a Ffowcs-Williams/Hawkings calculation. The results include wall-pressure, and far-field-noise intensities and spectra. The wall pressure signals in the three simulations are very similar and, in a comparison published separately, agree well with experiment and other simulations. In the absence of experimental noise data, the attention is focused on internal quality checks, by varying the permeable Ffowcs-Williams/Hawkings calculation surface and then by using only the solid surface. An unexpected finding at these Mach numbers is an apparent strong role for quadrupoles, revealed by a typical deficit of 3 dB in the solid-surface results, relative to the permeable-surface results. The solid-surface approach has variants, related to the presence of the ceiling (a plane of symmetry), which can increase this error further; there is little consensus on the exact configuration of the solid surfaces in the Ffowcs-Williams/Hawkings calculation procedure. Tentative theoretical arguments suggest that a balance somewhat in favor of quadrupoles over dipoles is plausible at Mach 0.115. However, the scaling of sound with Mach number does not follow the eighth power, as quadrupoles do in theory: it is closer to the sixth power. This trend gives a muddled theoretical picture, but agrees with the scaling observed in experiments. If it is confirmed, this finding will complicate airframe-noise calculations, and prevent the attribution of noise to a given component of the aircraft. Progress in airframe-noise simulations appears real, but systematic grid-refinement studies and noise comparisons with experiment or other simulations have yet to occur, and the theoretical uncertainty is high.

Spalart, Philippe R.; Shur, Mikhail L.; Strelets, Mikhail Kh.; Travin, Andrey K.

2011-08-01

94

Observations of correlated broadband electrostatic noise and electron-cyclotron emissions in the plasma sheet. Technical report  

SciTech Connect

Electric field wave observations in the central plasma sheet of the earth's magnetosphere show the correlated occurrence of broadband electrostatic noise and electrostatic electron cyclotron harmonic emissions. A model is proposed in which the broadband emissions are electron acoustic waves generated by an observed low energy electron beam, and the cyclotron emissions are generated by the hot electron loss cone instability. The high degree of correlation between the two emissions is provided in the model by the presence of the cold electron beam population, which allows both of the plasma instabilities to grow.

Roeder, J.L.; Angelopoulos, V.; Baumjohann, W.; Anderson, R.R.

1991-11-15

95

Ambient Seismic Noise Levels of the Seafloor Borehole Broadband Seismic Observatories in the Northwestern Pacific  

NASA Astrophysics Data System (ADS)

In 2000 and 2001, the seafloor borehole seismological observatories WP-1 and WP-2 in the northwestern Pacific were successfully installed. The WP-1 site is in the west Philippine Basin west of the Kyushu-Palau Ridge. The WP-2 observatory is situated on a normal oceanic Mesozoic crust in the northwestern Pacific Basin. Both the observatories fill important observational gaps, since no other land site can replace this site. Each observatory has two identical broadband seismometers (Guralp, CMG-1T), which are cemented, near the bottom of the hole. All the necessary power for the WP-1 is supplied from the Lithium Battery System with a capacity of 5.2 kAh. For the WP-2 observatory, the Sea Water Battery (SWB) System mainly supplies the power to the system. Additional lithium batteries were used as a backup system. Both seismometers are operational, but we are operating only one seismometer for both the observatories to reduce the consuming power of the system. The WP-2 observatory was activated in October 2000 using an ROV KAIKO. In August 2001, the KAIKO re-visited the WP-2 site. From the first observation, we obtained about three-months continuous data (Oct. 29th, 2000 - Jan. 27th, 2001). The KAIKO visited the WP-2 site again in June 2002 and approximately eleven-months continuous data (Aug. 3rd, 2001 - Jun. 29th, 2002) were retrieved for second observation period. The KAIKO also recovered the monitoring data for the SWB system. It was confirmed that the SWB system continued working for almost one year. The observation at the WP-1 was started from March 2002. We now have the preliminary data (about 20 minutes long) from during the ROV dive for the activation. A re-visit of the WP-1 site is planned in October 2002. The long-term variations of broadband seismic noise spectra (3mHz - 10 Hz) in the northwestern Pacific Basin were revealed. The noise level above 10 s is stable all the year round. The vertical component of the WP-2 has the noise level about -145 db (re: 1 m**2/s**4/Hz). The noise level of the horizontal component in the WP-2 is lower than that of the vertical component (-160 db above 100 s). Because there is a possibility that this vertical sensor has damage, we activated the alternative seismometer and shut down the sensor that had been used during the previous ROV visit. Due to the low seismic noise environment, many events were recorded in the records. It is found that the noise level of the vertical sensor at the WP-1 reaches -180 db between 10 s and 100 s from the preliminary data.

Shinohara, M.; Kanazawa, T.; Araki, E.; Suyehiro, K.; Shiobara, H.; Yamada, T.; Nakahigashi, K.; Mikada, H.; Fukao, Y.

2002-12-01

96

Noise reduction in oversampled filter banks using predictive quantization  

Microsoft Academic Search

We introduce two methods for quantization noise reduction in oversampled filter banks. These methods are based on predictive quantization (noise shaping or linear prediction). It is demonstrated that oversampled noise shaping or linear predictive subband coders are well suited for subband coding applications where, for technological or other reasons, low-resolution quan- tizers have to be used. In this case, oversampling

Helmut Bölcskei; Franz Hlawatsch

2001-01-01

97

Experimental validation of boundary element methods for noise prediction  

Microsoft Academic Search

Experimental validation of methods to predict radiated noise is presented. A combined finite element and boundary element model was used to predict the vibration and noise of a rectangular box excited by a mechanical shaker. The predicted noise was compared to sound power measured by the acoustic intensity method. Inaccuracies in the finite element model shifted the resonance frequencies by

A. F. Seybert; Fred B. Oswald

1992-01-01

98

Noise predictions of a high bypass turbofan engine using the Lockheed Near-Field Noise Prediction Program  

Microsoft Academic Search

The prediction of engine noise during cruise using the Near-Field Noise Prediction Program developed by Lockheed is examined. Test conditions were established which simulate the operation of a high bypass turbofan engine under a wide range of operating conditions. These test conditions include variations in altitude, flight Mach number and thrust setting. Based on the results of noise prediction made

J. W. Rawls Jr.

1986-01-01

99

Research at DLR towards airframe noise prediction and reduction  

Microsoft Academic Search

In the final approach phase airframe noise represents the ultimate aircraft noise barrier for future aircraft when equipped with quiet UHBR engines. This paper summarizes the results achieved at DLR in the development of methods and tools for airframe noise prediction and reduction. Numerous DLR internal, national and EC co-financed research projects were conducted to investigate the aerodynamic noise of

Werner Dobrzynski; Roland Ewert; Michael Pott-Pollenske; Michaela Herr; Jan Delfs

2008-01-01

100

Hybrid methods for airframe noise numerical prediction  

NASA Astrophysics Data System (ADS)

This paper describes some significant steps made towards the numerical simulation of the noise radiated by the high-lift devices of a plane. Since the full numerical simulation of such configuration is still out of reach for present supercomputers, some hybrid strategies have been developed to reduce the overall cost of such simulations. The proposed strategy relies on the coupling of an unsteady nearfield CFD with an acoustic propagation solver based on the resolution of the Euler equations for midfield propagation in an inhomogeneous field, and the use of an integral solver for farfield acoustic predictions.

Terracol, M.; Manoha, E.; Herrero, C.; Labourasse, E.; Redonnet, S.; Sagaut, P.

2005-07-01

101

a Unified Description of Time Dependence of Information Entropy Production and Flux in Thermal Broadband Noise-Driven Dynamical Systems  

Microsoft Academic Search

In this paper we have studied the dynamics of thermal broadband noise-driven dynamical system in terms of information entropy at both the nonstationary and stationary states. Here, a unified description of fluctuating force is considered in a thermodynamically closed system. Based on the Fokker-Planck description of stochastic processes and the entropy balance equation, we have calculated the time-dependence of the

Pradip Majee; Gurupada Goswami; Debashis Barik; Bidhan Chandra Bag

2009-01-01

102

Broadband signal processing for detection, classification, and identification of underwater, bottomed, and buried targets in ambient noise environments  

NASA Astrophysics Data System (ADS)

This paper addresses the theories, experiments and real data of passive detection, classification and identification of "silent" targets in the illumination of ambient noise, a method known as "Acoustic Daylight." A great deal of work and sonar systems exist on active and passive sonar systems, but the principle of using ambient noise as the sole source of acoustic illumination was explored with limited success. This paper presents some of the successes using broadband signal processing and theory of target resonance as proposed in Uricks' text. In addition, the paper will present some of the results from experiments and simulations and Navy data of opportunities.

Goo, Gee-In

2006-06-01

103

A boundary-element method using broadband vibrating-wall sources to predict high-frequency interior sound fields produced by wall vibration  

NASA Astrophysics Data System (ADS)

In the high-frequency limit, vibrating panels subject to spatially random, temporally broadband forcing are shown to have broadband power and directivity properties than can be characterized by a limited set of parameters, based on numerical simulations. The radiated pressure field is parametrized in terms of direction, wave speed ratio, panel damping, and dimensionless frequency. A source directivity equation dependent on these variables is presented. The radiation properties of this equation are incorporated to simulate vibrating wall panels in an energy/intensity-based boundary-element method (BEM) developed for the prediction of steady-state, broadband, reverberant sound fields in enclosures having either diffusely or specularly reflecting boundaries. The BEM method uses uncorrelated broadband directional intensity sources to construct the source and reflection sound fields and predict mean-square pressure distributions in enclosures. Because uncorrelated broadband directional intensity sources are used, the system does not require a frequency-by-frequency-based solution, thereby reducing computational expense. Simulations are compared to exact solutions obtained by computationally expensive frequency-by-frequency modal methods. When fully developed, the directed application of this method is aircraft interior noise caused by exterior boundary layer excitation on fuselage panels.

Franzoni, Linda P.; Duvall, Tracy A.

2005-09-01

104

Prevision du Bruit Externe des Helicopteres: Les Methodes Numeriques Vues Par UN Industriel (Predicting Helicopter External Noise: Numerical Methods as Conceived by an Industrialist).  

National Technical Information Service (NTIS)

This paper investigates the methods used for rotor rotational noise, impulsive noise from blade/vortex interaction, high speed noise, rotor broadband noise, the various types of fenestron noise, and noise from the turboshaft engines. From the helicopter m...

F. Toulmay D. Falchero G. Arnaud

1995-01-01

105

High-speed propeller noise prediction - A multidisciplinary approach  

Microsoft Academic Search

The prediction of noise produced by advanced propellers is a multidisciplinary subject which involves the aeroelasticity, aerodynamics, and aeroacoustics of rotating blades. As part of the PTA (Propfan Test Assess- ment) noise-prediction project of NASA Langley, state-of-the-art computational methods in these disciplines were combined to form a comprehensive propeller noise-prediction package. The primary function of the project was to assess

Mark H. Dunn; F. Farassat

1992-01-01

106

An investigation of list equivalency of the northwestern university auditory test no. 6 in interrupted broadband noise.  

PubMed

The equivalency of Lists 1 to 4 of the Northwestern University Auditory Test No. 6 (NU-6; T. W. Tillman and R. Carhart, 1966) was investigated in interrupted broadband noise. Forty-eight young adults with normal hearing participated. All lists were administered at 50 dB sensation level re: listener spondee recognition thresholds at signal-to-noise ratios (S/Ns) of 10, 5, 0, -5, -10, -15, -20, -25, and -30 dB. Significant differences in listener performance were observed only at S/Ns ranging from 10 to -10. Significant mean list differences varied from 5.8% to 12.0%. These findings support the notion that caution should be exercised in the interpretation of listener performance differences with NU-6 stimuli presented in a background of interrupted noise. PMID:15248801

Stuart, Andrew

2004-06-01

107

Impact of various noises on maximum reach in broadband light source based high-capacity WDM passive optical networks.  

PubMed

We investigated the effects of various noises on the performance of extended-reach WDM-PONs based on broadband light sources (BLSs). The maximum reach in BLS based WDM-PONs was analyzed by taking into account the impact of relative intensity noise of optical source, chromatic dispersion of transmission fiber and in-band crosstalk. We confirmed that the system's performance of BLS based WDM-PONs would be strongly dependent on the equivalent optical bandwidth of optical source. From the results, we found that the maximum reach in BLS based WDM-PONs operating at 1.25 Gb/s could be increased to be approximately 70 km of single-mode fiber as long as the chirp and relative intensity noise (RIN) of optical source would be suppressed properly. PMID:20588835

Kim, Chul Han

2010-05-10

108

Assessment and prediction of wind turbine noise.  

National Technical Information Service (NTIS)

The significance of basic aerodynamic noise sources for wind turbine noise are assessed, using information on the aero-acoustic mechanisms of other rotors, which have been studied in depth for many years. From the analysis, areas of potential improvement ...

M. V. Lowson

1993-01-01

109

A practical approach to helicopter internal noise prediction  

Microsoft Academic Search

A practical and well correlated procedure for predicting helicopter internal noise is presented. It accounts for the propagation of noise along multiple paths on an octave by octave basis. The method is sufficiently general to be applicable to conventional helicopters as well as other aircraft types, when the appropriate structural geometry, noise source strengths, and material acoustic properties are defined.

L. S. Levine; J. J. Defelice

1978-01-01

110

A Statistical Model for Gears Noise Prediction in Gearbox  

Microsoft Academic Search

This paper develops a statistical model for gears noise prediction in gearbox. Experimental study is made to detect the relationship between the errors in gear manufacturing and transmission gear noise by means of online noise test bench. Based on the experimental statistics, a multiple linear regression model is developed showing the relationship between the errors in gear manufacturing and transmission

Cheng Guangming; Xu Yudong

2010-01-01

111

Basilar-membrane responses to broadband noise modeled using linear filters with rational transfer functions.  

PubMed

Basilar-membrane responses to white Gaussian noise were recorded using laser velocimetry at basal sites of the chinchilla cochlea with characteristic frequencies near 10 kHz and first-order Wiener kernels were computed by cross correlation of the stimuli and the responses. The presence or absence of minimum-phase behavior was explored by fitting the kernels with discrete linear filters with rational transfer functions. Excellent fits to the kernels were obtained with filters with transfer functions including zeroes located outside the unit circle, implying nonminimum-phase behavior. These filters accurately predicted basilar-membrane responses to other noise stimuli presented at the same level as the stimulus for the kernel computation. Fits with all-pole and other minimum-phase discrete filters were inferior to fits with nonminimum-phase filters. Minimum-phase functions predicted from the amplitude functions of the Wiener kernels by Hilbert transforms were different from the measured phase curves. These results, which suggest that basilar-membrane responses do not have the minimum-phase property, challenge the validity of models of cochlear processing, which incorporate minimum-phase behavior. PMID:20542757

Recio-Spinoso, Alberto; Fan, Yun-Hui; Ruggero, Mario A

2010-06-10

112

Comparison of Measured and Predicted Airfoil Self-Noise with Application to Wind Turbine Noise Reduction.  

National Technical Information Service (NTIS)

In the ongoing JOULE-III project Development of Design Tools for Reduced Aerodynamic Noise Wind Turbines (DRAW), prediction codes for inflow-turbulence (IT) noise and turbulent boundary layer trailing-edge (TE) noise, are developed and validated. It is sh...

T. Dassen R. Parchen G. Guidati S. Wagner S. Kang A. E. Khodak

1997-01-01

113

The Prediction of Airframe Noise and Comparison with Experiment  

NASA Astrophysics Data System (ADS)

The success of the high bypass ratio turbofan engine in reducing the external noise of civil transport aircraft at take-off and landing, while improving the economics of air travel, has opened up the debate as to how much further it will be possible to reduce aircraft noise by the introduction of new aircraft or existing aircraft retrofitted with new engines. Irrespective of what new technology can offer in respect of further engine noise reduction for no loss of performance, it is now clear that all future aircraft will require airframe noise to be reduced on the approach, since today it is comparable with engine noise. This paper discusses the major components of airframe noise and reviews the present state of airframe noise prediction. Finally, a comparison is made between prediction and experimental data and the prospects for airframe noise reduction.

Lilley, G. M.

2001-01-01

114

Vortical gust boundary condition for realistic rotor wake/stator interaction noise prediction using computational aeroacoustics  

NASA Astrophysics Data System (ADS)

In this work, the NASA Glenn Research Center Broadband Aeroacoustic Stator Simulation (BASS) code is extended for use in the prediction of noise produced by realistic three-dimensional rotor wakes impinging on a downstream stator row. In order to accurately simulate such a flow using a nonlinear time-accurate solver, the inflow and outflow boundary conditions must simultaneously maintain the desired mean flow, allow outgoing vortical, entropic, and acoustic waves to cleanly exit the domain, and accurately impose the desired incoming flow disturbances. This work validates a new method for the acoustics-free imposition of three-dimensional vortical disturbances using benchmark test cases.

Hixon, Ray; Sescu, Adrian; Sawyer, Scott

2011-08-01

115

Noise prediction and control of Pudong International Airport expansion project  

Microsoft Academic Search

The Environmental Impact Assessment (EIA) process of the third runway building project of Pudong International Airport is\\u000a briefly introduced in the paper. The basic principle, the features, and the operation steps of newly imported FAA’s Integrated\\u000a Noise Model (INM) are discussed for evaluating the aircraft noise impacts. The prediction of the aircraft noise and the countermeasures\\u000a for the noise mitigation

Bin Lei; Xin Yang; Jianguo Yang

2009-01-01

116

Effect of White-Noise Correction on Linear Predictive Coding  

Microsoft Academic Search

White-noise correction is a technique used in speech coders using linear predictive coding (LPC). This technique generates an artificial noise-floor in order to avoid stability problems caused by numerical round-off errors. In this letter, we study the effect of white-noise correction on the roots of the LPC model. The results demonstrate in analytic form the relation between the noise floor

Tom Bäckström; Carlo Magi

2007-01-01

117

Supersonic jet noise prediction and noise source investigation for realistic baseline and chevron nozzles based on hybrid RANS/LES simulations  

NASA Astrophysics Data System (ADS)

Jet noise simulations have been performed for a military-style baseline nozzle and a chevron nozzle with design Mach numbers of Md = 1:5 operating at several off-design conditions. The objective of the current numerical study is to provide insight into the noise generation mechanisms of shock-containing supersonic hot jets and the noise reduction mechanisms of chevron nozzles. A hybrid methodology combining advanced CFD technologies and the acoustic analogy is used for supersonic jet noise simulations. Unsteady Reynolds-averaged Navier-Stokes (URANS) equations are solved to predict the turbulent noise sources in the jet flows. A modified version of the Detached Eddy Simulation (DES) approach is used to avoid excessive damping of fine scale turbulent fluctuations. A multiblock structured mesh topology is used to represent complex nozzle geometries, including the faceted inner contours and finite nozzle thickness. A block interface condition is optimized for the complex multiblock mesh topology to avoid the centerline singularity. A fourth-order Dispersion-Relation-Preserving (DRP) scheme is used for spatial discretization. To enable efficient calculations, a dual time-stepping method is used in addition to parallel computation using MPI. Both multigrid and implicit residual smoothing are used to accelerate the convergence rate of sub-iterations in the fictitious time domain. Noise predictions are made with the permeable surface Ffowcs Williams and Hawkings (FWH) solution. All the numerical methods have been implemented in the jet flow simulation code "CHOPA" and the noise prediction code "PSJFWH". The computer codes have been validated with several benchmark cases. A preliminary study has been performed for an under-expanded baseline nozzle jet with Mj = 1:56 to validate the accuracy of the jet noise simulations. The results show that grid refinement around the jet potential core and the use of a lower artificial dissipation improve the resolution of the predicted high frequency noise spectra. The results also show that the predicted low frequency noise spectra are sensitive to the axial extent of the acoustic data surface, and the high frequency noise spectra are affected by the radial size of the acoustic data surface. The baseline nozzle has been studied at several off-design conditions with Mj = 1:36, 1.47 and 1.56. Although the noise levels at mid to high frequencies are over-predicted at several shallow polar angles, the predicted noise spectra in the peak noise radiation direction and upstream directions agree very well with the experimental measurements. More encouraging is that the frequencies and amplitudes of the broadband shock-associated noise (BBSAN) are captured accurately at all three operating conditions. Three techniques are used to examine the noise source characteristics. The two-point space-time correlation method is used to analyze the statistical characteristics of the turbulent eddies. The direct flow-acoustic correlation technique and the beamformed acoustic pressures are used to reveal the different noise generation mechanisms of the large-scale and fine-scale turbulent fluctuations. The chevron nozzle simulations have been performed at the same operating conditions to evaluate the noise reduction effects. Special treatments are proposed to address the numerical difficulties caused by the chevrons. The impact of chevrons on the near-field noise sources and far-field noise radiation is simulated using the immersed boundary method (IBM) to overcome the great difficulties in grid generation. A non-matching block interface condition is developed to allow the grids to be greatly refined around chevrons for a higher accuracy of simulations without increasing the mesh size significantly. The predicted noise spectra agree very well with the acoustic measurements of the baseline nozzle, considering the small noise reductions of the chevrons at the given operating conditions. No apparent over-prediction is observed. However, the noise reductions are over-predicted because of the over-pr

Du, Yongle

118

SEMICONDUCTOR INTEGRATED CIRCUITS: A 0.18 ?m CMOS 3-5 GHz broadband flat gain low noise amplifier  

NASA Astrophysics Data System (ADS)

A 3-5 GHz broadband flat gain differential low noise amplifier (LNA) is designed for the impulse radio ultra-wideband (IR-UWB) system. The gain-flatten technique is adopted in this UWB LNA. Serial and shunt peaking techniques are used to achieve broadband input matching and large gain-bandwidth product (GBW). Feedback networks are introduced to further extend the bandwidth and diminish the gain fluctuations. The prototype is fabricated in the SMIC 0.18 ?m RF CMOS process. Measurement results show a 3-dB gain bandwidth of 2.4-5.5 GHz with a maximum power gain of 13.2 dB. The excellent gain flatness is achieved with ±0.45 dB gain fluctuations across 3-5 GHz and the minimum noise figure (NF) is 3.2 dB over 2.5-5 GHz. This circuit also shows an excellent input matching characteristic with the measured S11 below -13 dB over 2.9-5.4 GHz. The input-referred 1-dB compression point (IP1dB) is -11.7 dBm at 5 GHz. The differential circuit consumes 9.6 mA current from a supply of 1.8 V.

Lisong, Feng; Lu, Huang; Xuefei, Bai; Tianzuo, Xi

2010-02-01

119

Analysis and modeling of impulsive noise in broad-band powerline communications  

Microsoft Academic Search

Contrary to many other communication channels, the powerline channel does not represent an additive white Gaussian noise environment. In the frequency range from several hundred kilohertz up to 20 MHz, it is mostly dominated by narrow-band interference and impulsive noise. In particular, the impulsive noise introduces significant time variance into the powerline channel. Spectral analysis and time-domain analysis of impulsive

Manfred Zimmermann; Klaus Dostert

2002-01-01

120

“Buzz-saw” noise: A comparison of measurement with prediction  

NASA Astrophysics Data System (ADS)

Accurate prediction of “buzz-saw” noise in a turbofan inlet duct necessitates consideration of nonlinear acoustics, modelling a complete fan blade set, modelling an acoustic liner, and calculations at high frequencies. A recent series of papers has described new work concerning the application of one-dimensional propagation models to the prediction of buzz-saw noise. A numerical model, termed the frequency domain numerical solution or FDNS, has been developed. It can be used to calculate the nonlinear propagation of the rotor-alone pressure field in either a rigid or acoustically-lined inlet duct. From this the in-duct noise level of the buzz-saw tones can be determined. In previous work, validation of this method by comparison with in-duct noise measurements has been limited to rigid inlet ducts, because of the lack of availability of suitable measurements from lined ducts. In this article new measurements of buzz-saw noise in an acoustically-lined inlet duct are utilized. A comparison of measurements of buzz-saw noise in a lined inlet duct, and noise predictions from numerical simulations by the FDNS is presented. The detailed measurements reveal the effect of an acoustic liner on buzz-saw noise. The suitability of the numerical model to be used to provide realistic noise predictions for supersonic ducted fans is also examined.

McAlpine, A.; Fisher, M. J.; Tester, B. J.

2006-03-01

121

Geoacoustic inversion by using broadband ship noise recorded on the New Jersey Shelf  

Microsoft Academic Search

During the New Jersey Shelf RAGS03 experiment, acoustic signals emitted by ships of opportunity (merchant ships) are simultaneously recorded on three vertical line arrays (VLAs) and a horizontal line array (HLA). Recorded broadband (50-750 Hz) acoustic data sets are used to demonstrate the source localization capability as well as geoacoustic inversion capability. Waveguide invariant theory applied to beamforming by two

Altan Turgut

2005-01-01

122

Predicting tonal noise from a high rotational speed centrifugal fan  

NASA Astrophysics Data System (ADS)

Prediction of noise generated by centrifugal fans is much more complex than prediction noise generated by axial fans. A complete, aerodynamic and aeroacoustic, investigation of the tonal noise of a high rotational speed centrifugal fan is proposed in this paper. The studied fan is made up of an impeller, a diffuser and a return channel. The purpose of this work is to understand the nature of noise generated within this type of machine. An aeroacoustic model based on the Ffowcs Williams and Hawkings equation is used to predict dipole and monopole tonal noises in the frequency domain. Showing the importance of the monopole source in this kind of fans constitutes the main contribution in these research tasks. A numerical simulation of the fluid flow validated by experiments, enables to obtain the fluctuating forces and normal velocity on the impeller and diffuser blades needed for the aeroacoustic computation.

Khelladi, S.; Kouidri, S.; Bakir, F.; Rey, R.

2008-06-01

123

Long Wave TE/TM Noise Prediction Model.  

National Technical Information Service (NTIS)

A computer model that predicts both horizontally and vertically polarized noise in the ELF to LF band (10 Hz-60 kHz) is described. Since naturally occurring radio noise in this band is produced by lightning, and propagates to the receiver via the earth-io...

C. R. Warber E. C. Field

1993-01-01

124

Model tail rotor noise study in the DNW - Measured acoustics, blade pressures, noise predictions  

Microsoft Academic Search

The acoustic characteristics of the BO 105 model rotor have been measured in a wind tunnel experiment, and the results are reported. Emphasis is given to the main rotor\\/tail rotor interference noise. Simultaneously measured tail rotor blade surface pressures are presented and used to interpret the test results and as input for tail rotor noise predictions.

Klaus-J. Schultz; Wolf R. Splettstoesser

1992-01-01

125

Model tail rotor noise study in the DNW - Measured acoustics, blade pressures, noise predictions  

NASA Astrophysics Data System (ADS)

The acoustic characteristics of the BO 105 model rotor have been measured in a wind tunnel experiment, and the results are reported. Emphasis is given to the main rotor/tail rotor interference noise. Simultaneously measured tail rotor blade surface pressures are presented and used to interpret the test results and as input for tail rotor noise predictions.

Schultz, Klaus-J.; Splettstoesser, Wolf R.

1992-09-01

126

Transmission of Gear Noise to Aircraft Interiors Prediction Methods.  

National Technical Information Service (NTIS)

Prediction of interior noise of helicopters due to drive train vibration ideally requires an analytical model of the entire dynamic system including airframe, transmission, and all attachments. This paper addresses the need for such a model and certain of...

A. Berman

1985-01-01

127

Computational AeroAcoustics for Fan Noise Prediction.  

National Technical Information Service (NTIS)

An overview of the current state-of-the-art in computational aeroacoustics as applied to fan noise prediction at NASA Glenn is presented. Results from recent modeling efforts using three dimensional inviscid formulations in both frequency and time domains...

E. Envia R. Hixon R. Dyson

2002-01-01

128

Data Recovery from Seafloor Borehole Broadband Seismic Observatories in the Northwestern Pacific and Ambient Seismic NoiseLevel Changes  

NASA Astrophysics Data System (ADS)

In 2000 and 2001, the seafloor borehole seismological observatories WP-1 and WP-2 in the northwestern Pacific were installed. The WP-1 site is in the west Philippine Basin, and the WP-2 observatory is situated on a normal oceanic Mesozoic crust in the northwestern Pacific Basin. The seismic network with 1000-km interval in the western Pacific has been completed by the construction of these stations. Each observatory had two identical broadband seismometers (Guralp, CMG-1T), which were cemented in a igneous rock section. The WP-1 has a water depth of 5710m and all the necessary power was supplied from the Lithium Battery System. For the WP-2 observatory, a water depth is 5566m and the Sea Water Battery (SWB) System mainly supplied the power to the system. We operated only one seismometer for both the observatories to reduce the consuming power of the system. The WP-1 observatory was activated in March 2002 using the ROV KAIKO and long-term observation was started. In June 2006, the new ROV KAIKO-7000II dived to the WP-1 (fourth visit) and recovered the data. At this visit, data recording was discontinued. At present, seismic records of 692-days (Mar. 2002 - Feb, 2004) have been obtained from the WP-1. The WP-2 observatory was activated in October 2000 using the KAIKO. In June 2005, the KAIKO-7000II made fourth visit to the WP-2 and recovered the data. Recording at the WP-2 has been suspended from the fourth ROV visit. In total, 436-days data (Oct. 2000 - Jan. 2001, Aug. 2001 - July 2002) were retrieved. In addition, it was confirmed that the SWB system continued working for the whole observation period by the system monitoring data. The long-term variations of broadband seismic noise spectra (3mHz - 10 Hz) in oceanic basins were revealed. The noise levels (-160 db, re: 1 m**2/s**4/Hz) at periods of greater than 10 s are stable. On the other hand, temporal small variations (maximum fluctuation is 10 dB) of noise levels (-120 db) for periods around a few seconds are found. In these periods, the WP-1 station has large noises in summer and fall. The WP-2 station becomes noisy in winter. These suggest that the noise levels in these periods are related with weather and sea condition.

Shinohara, M.; Araki, E.; Kanazawa, T.; Suyehiro, K.; Yamada, T.; Mochizuki, K.; Nakahigashi, K.

2006-12-01

129

Heavy-Tailed Prediction Error: A Difficulty in Predicting Biomedical Signals of 1/f Noise Type  

PubMed Central

A fractal signal x(t) in biomedical engineering may be characterized by 1/f noise, that is, the power spectrum density (PSD) divergences at f = 0. According the Taqqu's law, 1/f noise has the properties of long-range dependence and heavy-tailed probability density function (PDF). The contribution of this paper is to exhibit that the prediction error of a biomedical signal of 1/f noise type is long-range dependent (LRD). Thus, it is heavy-tailed and of 1/f noise. Consequently, the variance of the prediction error is usually large or may not exist, making predicting biomedical signals of 1/f noise type difficult.

Li, Ming; Zhao, Wei; Chen, Biao

2012-01-01

130

“Buzz-saw” noise: A comparison of measurement with prediction  

Microsoft Academic Search

Accurate prediction of “buzz-saw” noise in a turbofan inlet duct necessitates consideration of nonlinear acoustics, modelling a complete fan blade set, modelling an acoustic liner, and calculations at high frequencies. A recent series of papers has described new work concerning the application of one-dimensional propagation models to the prediction of buzz-saw noise. A numerical model, termed the frequency domain numerical

A. McAlpine; M. J. Fisher; B. J. Tester

2006-01-01

131

``Buzz-saw'' noise: A comparison of measurement with prediction  

Microsoft Academic Search

Accurate prediction of ``buzz-saw'' noise in a turbofan inlet duct necessitates consideration of nonlinear acoustics, modelling a complete fan blade set, modelling an acoustic liner, and calculations at high frequencies. A recent series of papers has described new work concerning the application of one-dimensional propagation models to the prediction of buzz-saw noise. A numerical model, termed the frequency domain numerical

A. McAlpine; M. J. Fisher; B. J. Tester

2006-01-01

132

Sound propagation and the prediction of railway noise  

NASA Astrophysics Data System (ADS)

The propagation of sound from moving trains is considered in terms of existing railway noise prediction methods and in the light of those improvements that can be expected in these methods over the next decade or so. The topic is approached from the point of view of the noise control engineer, who requires a reliable tool for estimating the long-term noise impact and a method for determining the effects of noise reduction measures. An attempt is made at listing research areas which will provide the foundation for future improvements in the prediction methods and in our understanding of outdoor sound propagation. Large parts of the paper are also relevant for noise sources other than trains.

Ringheim, M.

1988-01-01

133

On the prediction of wayside noise levels for high-speed railway vehicles  

Microsoft Academic Search

The relative contributions of aerodynamic and wheel\\/rail noise to railway wayside noise levels are not well understood. Methods for predicting these contributions discussed in this paper include an equation for turbulent boundary layer noise (the minimum wayside noise), an empirical formula for total aerodynamic noise based on airframe noise studies, and the Peters equation for wheel\\/rail interaction noise. Comparisons are

W. F. King III

1976-01-01

134

Temporal Variation of Ambient Seismic Noise of the Seafloor Borehole Broadband Seismic Observatory WP-1 in the West Philippine Basin  

NASA Astrophysics Data System (ADS)

The seafloor borehole seismological observatory WP-1 is positioned in the west Philippine Basin west of the Kyushu-Palau Ridge. The observatory was installed in April 2001 to fill observational gaps for global seismological networks. The two identical seismometers (Guralp Systems Ltd., CMG-1T) were cemented into the hole as required to assure good coupling. All the necessary power is supplied from lithium batteries. The system has two units of batteries. The data recorder and control unit are placed on the sea floor and a remote operated vehicle (ROV) services the station. We usually operated only one seismometer to reduce the consuming power of the system. The WP-1 observatory was activated in March 2002 using an ROV KAIKO and long-term observation was started using first lithium battery unit. In October 2002, the KAIKO re-visited the WP-1 site and we obtained about six-months continuous data (Mar. 26th, 2002 - Oct. 6th, 2002). The KAIKO visited the WP-1 site again in May 2003 and seven-months continuous data (Oct. 7th, 2002 - May. 7th, 2003) were retrieved. During the third visit, the KAIKO changed an electric connection and the second battery unit started to supply the power to the system. At present, seismic records of 408 days in total have been obtained from the WP-1 observatory. The long-term variations of broadband seismic noise spectra (3mHz - 10 Hz) in the west Philippine Basin were revealed. The noise levels at periods of greater than 10 s are stable all the year round. It is found that the noise levels of the vertical component at the WP-1 reach -180 db (re: 1 m**2/s**4/Hz) at periods between 10 s and 100 s. On the other hand, temporal small variations (maximum fluctuation is 10 dB) of noise levels for periods around a few seconds are seen; the WP-1 station has large noises in summer and fall. The small island (Okinotori-shima) lies about 100 km northeast of the WP-1. The meteorological station is being operated at Okinotori-shima and we can compare the meteorological data at Okinotori-shima and the noise spectrum of the WP-1. The speed of wind looks to be related with the noise levels for periods around a few second.

Shinohara, M.; Kanazawa, T.; Araki, E.; Suyehiro, K.; Yamada, T.; Mochizuki, K.; Shiobara, H.; Nakahigashi, K.; Mikada, H.; Fukao, Y.

2003-12-01

135

Prediction of helicopter rotor noise from measured blade surface pressure  

NASA Astrophysics Data System (ADS)

The current techniques of helicopter rotor noise prediction attempt to describe the details of the noise field precisely and remove the empiricisms and restrictions inherent in previous methods. These techniques require detailed inputs of the rotor geometry, operating conditions, and blade surface pressure distribution. The purpose of this paper is to review those techniques in general and the Farassat/Nystrom analysis in particular. The predictions of the Farassat/Nystrom noise computer program, using both measured and calculated blade surface pressure data, are compared to measured noise level data. This study is based on a contract from NASA to Bolt Beranek and Newman Inc. (BBN) with measured data from the AH-lG Helicopter Operational Loads Survey flight test program supplied by Bell Helicopter Textron.

Succi, G. P.; Brieger, J. T.

136

CONTROL OF AIRCRAFT INTERIOR BROADBAND NOISE WITH FOAM-PVDF SMART SKIN  

Microsoft Academic Search

A foam-PVDF smart skin design for aircraft interior noise control is discussed. The smart skin is designed to reduce sound by the action of the passive absorption of an acoustic foam (which is effective at higher frequencies) and the active input of a PVDF element driven by an oscillating electrical input (which is effective at lower frequencies). For performance testing,

C. Guigou; C. R. Fuller

1999-01-01

137

Robust broadband control of acoustic noise in ducts: a passivity-based approach  

Microsoft Academic Search

Control of acoustic systems is a challenging problem for several reasons. Some primary reasons include computational complexity resulting from very high-order models, non- minimum phase behavior introduced by finite dimensional approximations and transportation delays, uncertainties introduced by non-uniform boundary conditions, and acoustic interaction with the dynamics of the enclosure structure. Until recently, most active noise control techniques focused on feedforward

A. G. Kelkar; H. R. Pota

2003-01-01

138

Downwind rotor horizontal axis wind turbine noise prediction  

NASA Astrophysics Data System (ADS)

NASA and industry are currently cooperating in the conduct of extensive experimental and analytical studies to understand and predict the noise of large, horizontal axis wind turbines. This effort consists of (1) obtaining high quality noise data under well controlled and documented test conditions, (2) establishing the annoyance criteria for impulse noise of the type generated by horizontal axis wind turbines with rotors downwind of the support tower, (3) defining the wake characteristics downwind of the axial location of the plane of rotation, (4) comparing predictions with measurements made by use of wake data, and (5) comparing predictions with annoyance criteria. The status of work by Hamilton Standard in the above areas which was done in support of the cooperative NASA and industry studies is briefly summarized.

Metzger, F. B.; Klatte, R. J.

1981-05-01

139

Predicting perception in noise using cortical auditory evoked potentials.  

PubMed

Speech perception in background noise is a common challenge across individuals and health conditions (e.g., hearing impairment, aging, etc.). Both behavioral and physiological measures have been used to understand the important factors that contribute to perception-in-noise abilities. The addition of a physiological measure provides additional information about signal-in-noise encoding in the auditory system and may be useful in clarifying some of the variability in perception-in-noise abilities across individuals. Fifteen young normal-hearing individuals were tested using both electrophysiology and behavioral methods as a means to determine (1) the effects of signal-to-noise ratio (SNR) and signal level and (2) how well cortical auditory evoked potentials (CAEPs) can predict perception in noise. Three correlation/regression approaches were used to determine how well CAEPs predicted behavior. Main effects of SNR were found for both electrophysiology and speech perception measures, while signal level effects were found generally only for speech testing. These results demonstrate that when signals are presented in noise, sensitivity to SNR cues obscures any encoding of signal level cues. Electrophysiology and behavioral measures were strongly correlated. The best physiological predictors (e.g., latency, amplitude, and area of CAEP waves) of behavior (SNR at which 50 % of the sentence is understood) were N1 latency and N1 amplitude measures. In addition, behavior was best predicted by the 70-dB signal/5-dB SNR CAEP condition. It will be important in future studies to determine the relationship of electrophysiology and behavior in populations who experience difficulty understanding speech in noise such as those with hearing impairment or age-related deficits. PMID:24030818

Billings, Curtis J; McMillan, Garnett P; Penman, Tina M; Gille, Sun Mi

2013-09-13

140

Basilar-Membrane Responses to Broadband Noise Modeled Using Linear Filters With Rational Transfer Functions  

Microsoft Academic Search

Basilar-membrane responses to white Gaussian noise were recorded using laser velocimetry at basal sites of the chinchilla cochlea with characteristic frequencies near 10 kHz and first-order Wiener kernels were computed by cross correlation of the stimuli and the responses. The presence or absence of minimum-phase behavior was explored by fitting the kernels with discrete linear filters with rational transfer functions.

Alberto Recio-Spinoso; Yun-Hui Fan; Mario A. Ruggero

2011-01-01

141

Control of Aircraft Interior Broadband Noise with Foam-Pvdf Smart Skin  

NASA Astrophysics Data System (ADS)

A foam-PVDF smart skin design for aircraft interior noise control is discussed. The smart skin is designed to reduce sound by the action of the passive absorption of an acoustic foam (which is effective at higher frequencies) and the active input of a PVDF element driven by an oscillating electrical input (which is effective at lower frequencies). For performance testing, the foam-PVDF smart skin is mounted in the cockpit of a Cessna Citation III fuselage. The fuselage crown panels are excited with a speaker located on the outside of the cockpit and driven by a band-limited random excitation. A MIMO feedforward Filtered-x LMS controller is implemented to minimize the error sensor signals provided by microphones in the close proximity of the smart skin elements. Three different reference signals are implemented for the feedforward controller and are compared in terms of the interior noise attenuation achieved. The voltage sent to the disturbance speaker provides an optimal reference signal which is not realistic in practice. Therefore, the use of either a structural sensor (accelerometer directly mounted on the fuselage) or an acoustic sensor (microphone located close to the fuselage) is investigated to supply a practical reference signal. The potential of the smart foam-PVDF skin for reducing interior noise is demonstrated.

Guigou, C.; Fuller, C. R.

1999-02-01

142

Application of high resolution airload calculations to helicopter noise prediction  

Microsoft Academic Search

Recent studies of blade\\/vortex interactions have resulted in the development of aerodynamic models with which the very detailed loading data necessary for noise predictions can be calculated. The methods employed not only obviate the need for some of the simplifying assumptions that have previously reduced the precision and sensitivity of acoustic calculations but also achieve this improvement at little cost

A. C. Pike

1987-01-01

143

Towards high performance computing for molecular structure prediction using IBM Cell Broadband Engine - an implementation perspective  

PubMed Central

Background RNA structure prediction problem is a computationally complex task, especially with pseudo-knots. The problem is well-studied in existing literature and predominantly uses highly coupled Dynamic Programming (DP) solutions. The problem scale and complexity become embarrassingly humungous to handle as sequence size increases. This makes the case for parallelization. Parallelization can be achieved by way of networked platforms (clusters, grids, etc) as well as using modern day multi-core chips. Methods In this paper, we exploit the parallelism capabilities of the IBM Cell Broadband Engine to parallelize an existing Dynamic Programming (DP) algorithm for RNA secondary structure prediction. We design three different implementation strategies that exploit the inherent data, code and/or hybrid parallelism, referred to as C-Par, D-Par and H-Par, and analyze their performances. Our approach attempts to introduce parallelism in critical sections of the algorithm. We ran our experiments on SONY Play Station 3 (PS3), which is based on the IBM Cell chip. Results Our results suggest that introducing parallelism in DP algorithm allows it to easily handle longer sequences which otherwise would consume a large amount of time in single core computers. The results further demonstrate the speed-up gain achieved in exploiting the inherent parallelism in the problem and also elicits the advantages of using multi-core platforms towards designing more sophisticated methodologies for handling a fairly long sequence of RNA. Conclusion The speed-up performance reported here is promising, especially when sequence length is long. To the best of our literature survey, the work reported in this paper is probably the first-of-its-kind to utilize the IBM Cell Broadband Engine (a heterogeneous multi-core chip) to implement a DP. The results also encourage using multi-core platforms towards designing more sophisticated methodologies for handling a fairly long sequence of RNA to predict its secondary structure.

2010-01-01

144

Gene expression variations are predictive for stochastic noise  

PubMed Central

Fluctuations in protein abundance among single cells are primarily due to the inherent stochasticity in transcription and translation processes, such stochasticity can often confer phenotypic heterogeneity among isogenic cells. It has been proposed that expression noise can be triggered as an adaptation to environmental stresses and genetic perturbations, and as a mechanism to facilitate gene expression evolution. Thus, elucidating the relationship between expression noise, measured at the single-cell level, and expression variation, measured on population of cells, can improve our understanding on the variability and evolvability of gene expression. Here, we showed that noise levels are significantly correlated with conditional expression variations. We further demonstrated that expression variations are highly predictive for noise level, especially in TATA-box containing genes. Our results suggest that expression variabilities can serve as a proxy for noise level, suggesting that these two properties share the same underlining mechanism, e.g. chromatin regulation. Our work paves the way for the study of stochastic noise in other single-cell organisms.

Dong, Dong; Shao, Xiaojian; Deng, Naiyang; Zhang, Zhaolei

2011-01-01

145

MJO empirical modeling and improved prediction by "Past Noise Forecasting"  

NASA Astrophysics Data System (ADS)

The Madden-Julian oscillation (MJO) is the dominant mode of intraseasonal variability in tropics and plays an important role in global climate. Here we presents modeling and prediction study of MJO by using Empirical Model Reduction (EMR). EMR is a methodology for constructing stochastic models based on the observed evolution of selected climate fields; these models represent unresolved processes as multivariate, spatially correlated stochastic forcing. In EMR, multiple polynomial regression is used to estimate the nonlinear, deterministic propagator of the dynamics, as well as multi-level additive stochastic forcing -"noise", directly from the observational dataset. The EMR approach has been successfully applied on the seasonal-to-interannual time scale for real-time ENSO prediction (Kondrashov et al. 2005), as well as atmospheric midlatitude intraseasonal variability (Kondrashov et al. 2006,2010). In this study nonlinear (quadratic) with annual cycle, three-level EMR model was developed to model and predict leading pair of real-time multivariate Madden-Julian oscillation (RMM1,2) daily indices (June 1974- January 2009, http://cawcr.gov.au/staff/mwheeler/maproom/RMM/). The EMR model captures essential MJO statistical features, such as seasonal dependence, RMM1,2 autocorrelations and spectra. By using the "Past Noise Forecasting" (PNF) approach developed and successfully applied to improve long-term ENSO prediction in Chekroun et al. (2011), we are able to notably improve the cross-validated prediction skill of RMM indices- especially at lead times of 15-to-30 days. The EMR/PNF method has two steps: (i) select noise samples - or "snippets" - from the past noise, which have forced the EMR model to yield the MJO phase resembling the one at the the currently observed state; and (ii) use these "noise" snippets to create ensemble forecast of EMR model. The MJO phase identification is based on Singular Spectrum Analysis reconstruction of 30-60 day MJO cycle.

Kondrashov, D. A.; Chekroun, M.; Robertson, A. W.; Ghil, M.

2011-12-01

146

Signal, noise, and bias for a broadband, division-of-amplitude Stokes polarimeter.  

PubMed

We analyze estimation error as a function of spectral bandwidth for division-of-amplitude (DoAm) Stokes polarimeters. Our approach allows quantitative assessment of the competing effects of noise and deterministic error, or bias, as bandwidth is varied.We use the signal-to-rms error (SRR) as a metric. Rather than calculating the SRR of the estimated Stokes parameters themselves, we use the singular-value decomposition to calculate the SRRs of the coefficients of the measured data vector projected onto the measurement matrix left singular vectors.We argue that calculating the SRRs for left singular vector coefficients will allow development of reconstruction filters to minimize Stokes estimation error. For the example case of a source with constant polarization over a relatively wide band, we show that as the spectral filter bandwidth is increased to include wavelengths significantly different than the design wavelength, the SRRs of the estimated left singular vector coefficients will a.) increase monotonically if relatively few photo-detection events (PDEs) are recorded, b.) after a sharp peak close to the design wavelength, decrease monotonically if relatively many PDEs are recorded, and c.) have well-defined maxima for nominal PDE counts. Given some idea of the source brightness relative to detector noise, one can specify a spectral filter bandwidth minimizing the variance and bias effects and optimizing Stokes parameter estimation. Our approach also allows one to specify the bandwidth over which the response of "achromatic" optics must be reasonably invariant with wavelength for rms Stokes estimation error to remain below some desired maximum. Finally, we point out that our method can be generalized not only to other types of polarimeters, but also to any sensing scheme that can be represented by a linear system for limiting values of a certain parameter. PMID:20721188

Tyler, David W; Mudge, Jason D

2010-08-16

147

A new approach to complete aircraft landing gear noise prediction  

NASA Astrophysics Data System (ADS)

This thesis describes a new landing gear noise prediction system developed at The Pennsylvania State University, called Landing Gear Model and Acoustic Prediction code (LGMAP). LGMAP is used to predict the noise of an isolated or installed landing gear geometry. The predictions include several techniques to approximate the aeroacoustic and aerodynamic interactions of landing gear noise generation. These include (1) a method for approximating the shielding of noise caused by the landing gear geometry, (2) accounting for local flow variations due to the wing geometry, (3) the interaction of the landing gear wake with high-lift devices, and (4) a method for estimating the effect of gross landing gear design changes on local flow and acoustic radiation. The LGMAP aeroacoustic prediction system has been created to predict the noise generated by a given landing gear. The landing gear is modeled as a set of simple components that represent individual parts of the structure. Each component, ranging from large to small, is represented by a simple geometric shape and the unsteady flow on the component is modeled based on an individual characteristic length, local flow velocity, and the turbulent flow environment. A small set of universal models is developed and applied to a large range of similar components. These universal models, combined with the actual component geometry and local environment, give a unique loading spectrum and acoustic field for each component. Then, the sum of all the individual components in the complete configuration is used to model the high level of geometric complexity typical of current aircraft undercarriage designs. A line of sight shielding algorithm based on scattering by a two-dimensional cylinder approximates the effect of acoustic shielding caused by the landing gear. Using the scattering from a cylinder in two-dimensions at an observer position directly behind the cylinder, LGMAP is able to estimate the reduction in noise due to shielding by the landing gear geometry. This thesis compares predictions with data from a recent wind tunnel experiment conducted at NASA Langley Research Center, and demonstrates that including the acoustic scattering can improve the predictions by LGMAP at all observer positions. In this way, LGMAP provides more information about the actual noise propagation than simple empirical schemes. Two-dimensional FLUENT calculations of approximate wing cross-sections are used by LGMAP to compute the change in noise due to the change in local flow velocity in the vicinity of the landing gear due to circulation around the wing. By varying angle of attack and flap deflection angle in the CFD calculations, LGMAP is able to predict the noise level change due to the change in local flow velocity in the landing gear vicinity. A brief trade study is performed on the angle of attack of the wing and flap deflection angle of the flap system. It is shown that increasing the angle of attack or flap deflection angle reduces the flow velocity in the vicinity of the landing gear, and therefore the predicted noise. Predictions demonstrate the ability of the prediction system to quickly estimate the change in landing gear noise caused by a change in wing configuration. A three-dimensional immersed boundary CFD calculation of simplified landing gear geometries provides relatively quick estimates of the mean flow around the landing gear. The mean flow calculation provides the landing gear wake geometry for the prediction of trailing edge noise associated with the interaction of the landing gear wake with the high lift devices. Using wind tunnel experiments that relate turbulent intensity to wake size and the Ffowcs Williams and Hall trailing edge noise equation for the acoustic calculation, LGMAP is able to predict the landing gear wake generated trailing edge noise. In this manner, LGMAP includes the effect of the interaction of the landing gear's wake with the wing/flap system on the radiated noise. The final prediction technique implemented includes local flow calculations of a landing gear wi

Lopes, Leonard V.

148

Prediction of the interaction noise emitted by helicopter fenestrons  

NASA Astrophysics Data System (ADS)

This paper is concerned with the sound generation from a helicopter fenestron due to rotor-stator interactions. Two mechanisms are investigated: (1) the rotor noise due to potential disturbances created by the cylindric struts (transmission shaft and support arm) located behind the rotorplane, and (2) the stator noise resulting from the interaction with the rotor viscous wakes. Each mechanism is theoretically analyzed. The models employed give a simple expression of the acoustic field without requiring adjustable parameters and thus can be used as prediction methods.

Fournier, Francette; Roger, Michel

1989-12-01

149

Prediction of flyover jet noise spectra from static tests  

NASA Astrophysics Data System (ADS)

A scaling law is derived for predicting the flyover noise spectra of a single-stream shock-free circular jet from static experiments. The theory is based on the Lighthill approach to jet noise. Density terms are retained to include the effects of jet heating. The influence of flight on the turbulent flow field is considered by an experimentally supported similarity assumption. The resulting scaling laws for the difference between one-third-octave spectra and the overall sound pressure level compare very well with flyover experiments with a jet engine and with wind tunnel experiments with a heated model jet.

Michel, U.; Michalke, A.

1981-12-01

150

Full prediction of the broadband optical modulation performance of a twisted nematic liquid crystal cell  

NASA Astrophysics Data System (ADS)

We present a procedure to obtain the physical parameters responsible of twisted nematic liquid crystal (LC) cells optical modulation. The novelty of our approach is based on the use of spectroscopic measurements of the light transmitted by the system polarizer LC cell-analyzer, combined with a previously proposed simple physical model of the LC twist and tilt distribution along cell. The procedure involves two steps: the first one yields off-state parameters like the LC director orientation, the twist angle, and the optical path difference (cell gap); the second step yields the effective retardances of the central and edge LC layers. The use of a spectroscopic method provides a full characterization of the LC cell as a function of both the voltage and the wavelength. The complete procedure leads to a very accurate prediction of the transmitted light broadband spectrum, as well as the complex (amplitude and phase) modulation for any wavelength within the calibration range.

Moreno, Ignacio; Cutillas, Ana M.; Sánchez-López, María M.; Velásquez, Pablo; Mateos, Felipe

2008-11-01

151

Prediction of broad-band strong ground motions from large subduction earthquakes using a characterized source model  

Microsoft Academic Search

In Japan, long-term probabilities of several large subduction earthquakes have been evaluated by the Headquaters for Earthquake Research Promotion. In order to mitigate the disaster caused by such earthquakes, it is very important to predict broad-band strong ground motions of engineering interest before events. A methodology has been proposed for estimating strong ground motions from scenario earthquakes caused by active

K. Kamae; H. Kawabe; K. Irikura

2002-01-01

152

Broadband ultrasound attenuation of the calcaneus predicts lumbar and femoral neck density in Caucasian women: A preliminary study  

Microsoft Academic Search

Recent studies have demonstrated the ability of ultrasound techniques to differentiate normal and osteoporotic women. To define the ability of broadband ultrasound attenuation (BUA) of the calcaneus to predict axial bone mass, the ultrasound value was correlated with lumbar vertebral and femoral neck density in 22 Caucasian women. The three measures of bone mass inversely correlated with age: lumbar density

D. T. Baran; Clare Kearns McCarthy; D. Leahey; R. Lew

1991-01-01

153

Cortical activity patterns predict robust speech discrimination ability in noise  

PubMed Central

The neural mechanisms that support speech discrimination in noisy conditions are poorly understood. In quiet conditions, spike timing information appears to be used in the discrimination of speech sounds. In this study, we evaluated the hypothesis that spike timing is also used to distinguish between speech sounds in noisy conditions that significantly degrade neural responses to speech sounds. We tested speech sound discrimination in rats and recorded primary auditory cortex (A1) responses to speech sounds in background noise of different intensities and spectral compositions. Our behavioral results indicate that rats, like humans, are able to accurately discriminate consonant sounds even in the presence of background noise that is as loud as the speech signal. Our neural recordings confirm that speech sounds evoke degraded but detectable responses in noise. Finally, we developed a novel neural classifier that mimics behavioral discrimination. The classifier discriminates between speech sounds by comparing the A1 spatiotemporal activity patterns evoked on single trials with the average spatiotemporal patterns evoked by known sounds. Unlike classifiers in most previous studies, this classifier is not provided with the stimulus onset time. Neural activity analyzed with the use of relative spike timing was well correlated with behavioral speech discrimination in quiet and in noise. Spike timing information integrated over longer intervals was required to accurately predict rat behavioral speech discrimination in noisy conditions. The similarity of neural and behavioral discrimination of speech in noise suggests that humans and rats may employ similar brain mechanisms to solve this problem.

Shetake, Jai A.; Wolf, Jordan T.; Cheung, Ryan J.; Engineer, Crystal T.; Ram, Satyananda K.; Kilgard, Michael P.

2012-01-01

154

Signal-to-Noise, Predictability Limits, and Seasonal Predictions  

NASA Astrophysics Data System (ADS)

Predictability limits for seasonal atmospheric climate variability depend on the fraction of variability that is due to factors external to the atmosphere (e.g., boundary conditions, atmospheric initial conditions etc.) and the fraction that is internal. From the analysis of observed data alone, however, separating the total seasonal atmospheric variance into its external and internal components is not feasible. In this paper a simple procedure for estimating atmospheric internal variability is outlined. This procedure is based on the expected value of the mean square error between the observed and the general circulation model simulated (or predicted) seasonal mean anomaly. The end result is a spatial map for the estimate of the observed seasonal atmospheric internal (or unpredictable) variability. As improved general circulation models become available, mean square error estimated from the new generation of general circulation models can be easily included in the procedure proposed herein, bringing the estimate for the internal variability closer to its true estimate.

Kumar, A.; Jha, B.; Zhang, Q.; Bounoua, L.

2006-05-01

155

Noise prediction of a subsonic turbulent round jet using the lattice-Boltzmann method.  

PubMed

The lattice-Boltzmann method (LBM) was used to study the far-field noise generated from a Mach, M(j)=0.4, unheated turbulent axisymmetric jet. A commercial code based on the LBM kernel was used to simulate the turbulent flow exhausting from a pipe which is 10 jet radii in length. Near-field flow results such as jet centerline velocity decay rates and turbulence intensities were in agreement with experimental results and results from comparable LES studies. The predicted far field sound pressure levels were within 2 dB from published experimental results. Weak unphysical tones were present at high frequency in the computed radiated sound pressure spectra. These tones are believed to be due to spurious sound wave reflections at boundaries between regions of varying voxel resolution. These "VR tones" did not appear to bias the underlying broadband noise spectrum, and they did not affect the overall levels significantly. The LBM appears to be a viable approach, comparable in accuracy to large eddy simulations, for the problem considered. The main advantages of this approach over Navier-Stokes based finite difference schemes may be a reduced computational cost, ease of including the nozzle in the computational domain, and ease of investigating nozzles with complex shapes. PMID:20815448

Lew, Phoi-Tack; Mongeau, Luc; Lyrintzis, Anastasios

2010-09-01

156

Frequency-domain prediction of turbofan noise radiation  

Microsoft Academic Search

This paper describes a frequency-domain numerical method for predicting noise radiation from ducted fans, including acoustic treatment and non-uniform background flow effects. The method solves the Euler equations linearized about a mean flow in the frequency domain. A pseudo-time derivative term is added to the frequency-domain equations so that a time marching technique can be employed to drive the acoustic

Y. Özyörük; E. Alpman; V. Ahuja; L. N. Long

2004-01-01

157

Simplified contact filters in wheel\\/rail noise prediction  

Microsoft Academic Search

When predicting rolling noise due to wheel and rail roughness a “contact filter” is generally applied to account for the effect of the finite size of the wheel\\/rail contact. For time-domain analysis these calculations must be fast enough to get results in a reasonable time. Remington and Webb have devised a versatile three-dimensional ‘distributed point reacting spring’ (DPRS) contact model

R. A. J. Ford; D. J. Thompson

2006-01-01

158

Simplified contact filters in wheel\\/rail noise prediction  

Microsoft Academic Search

When predicting rolling noise due to wheel and rail roughness a ``contact filter'' is generally applied to account for the effect of the finite size of the wheel\\/rail contact. For time-domain analysis these calculations must be fast enough to get results in a reasonable time. Remington and Webb have devised a versatile three-dimensional `distributed point reacting spring' (DPRS) contact model

R. A. J. Ford; D. J. Thompson

2006-01-01

159

Exterior noise prediction of light duty truck based on near-field acoustic holography  

Microsoft Academic Search

The basic principle of broadband acoustic holography based on intensity measurement (BAHIM) is demonstrated. Numerical simulation is made with point source as object, and reconstruction phase of the complex sound pressure is exactly obtained. The light duty truck manufactured by some Chinese auto manufacturer was tested with BAHIM, the radiated sound field of the noise source is forecasted, the far-field

Shuming Chen; Dengfeng Wang; Ankang Zuo; Zhen Chen

2010-01-01

160

Broadband teleportation  

NASA Astrophysics Data System (ADS)

Quantum teleportation of an unknown broadband electromagnetic field is investigated. The continuous-variable teleportation protocol by Braunstein and Kimble [Phys. Rev. Lett. 80, 869 (1998)] for teleporting the quantum state of a single mode of the electromagnetic field is generalized for the case of a multimode field with finite bandwith. We discuss criteria for continuous-variable teleportation with various sets of input states and apply them to the teleportation of broadband fields. We first consider as a set of input fields (from which an independent state preparer draws the inputs to be teleported) arbitrary pure Gaussian states with unknown coherent amplitude (squeezed or coherent states). This set of input states, further restricted to an alphabet of coherent states, was used in the experiment by Furusawa et al. [Science 282, 706 (1998)]. It requires unit-gain teleportation for optimizing the teleportation fidelity. In our broadband scheme, the excess noise added through unit-gain teleportation due to the finite degree of the squeezed-state entanglement is just twice the (entanglement) source's squeezing spectrum for its ``quiet quadrature.'' The teleportation of one half of an entangled state (two-mode squeezed vacuum state), i.e., ``entanglement swapping,'' and its verification are optimized under a certain nonunit gain condition. We will also give a broadband description of this continuous-variable entanglement swapping based on the single-mode scheme by van Loock and Braunstein [Phys. Rev. A 61, 10 302 (2000)].

van Loock, P.; Braunstein, Samuel L.; Kimble, H. J.

2000-08-01

161

An unsteady aerodynamic formulation for efficient rotor tonal noise prediction  

NASA Astrophysics Data System (ADS)

An aerodynamic/aeroacoustic solution methodology for predction of tonal noise emitted by helicopter rotors and propellers is presented. It is particularly suited for configurations dominated by localized, high-frequency inflow velocity fields as those generated by blade-vortex interactions. The unsteady pressure distributions are determined by the sectional, frequency-domain Küssner-Schwarz formulation, with downwash including the wake inflow velocity predicted by a three-dimensional, unsteady, panel-method formulation suited for the analysis of rotors operating in complex aerodynamic environments. The radiated noise is predicted through solution of the Ffowcs Williams-Hawkings equation. The proposed approach yields a computationally efficient solution procedure that may be particularly useful in preliminary design/multidisciplinary optimization applications. It is validated through comparisons with solutions that apply the airloads directly evaluated by the time-marching, panel-method formulation. The results are provided in terms of blade loads, noise signatures and sound pressure level contours. An estimation of the computational efficiency of the proposed solution process is also presented.

Gennaretti, M.; Testa, C.; Bernardini, G.

2013-12-01

162

Broadband sub-millimeter wave amplifer module with 38dB gain and 8.3dB noise figure  

NASA Astrophysics Data System (ADS)

Broadband sub-millimeter wave technology has received significant attention for potential applications in security, medical, and military imaging. Despite theoretical advantages of reduced size, weight, and power compared to current millimeter-wave systems, sub-millimeter-wave systems are hampered by a fundamental lack of amplification with sufficient gain and noise figure properties. We report on the development of a sub-millimeter wave amplifier module as part of a broadband pixel operating from 300-350 GHz, biased off of a single 2V power supply. Over this frequency range, > 38 dB gain and < 8.3 dB noise figure are obtained and represent the current state-of-art performance capabilities. The prototype pixel chain consists of two WR3 waveguide amplifier blocks, and a horn antenna and diode detector. The low noise amplifier Sub-Millimeter-wave Monolithic Integrated Circuit (SMMIC) was originally developed under the DARPA SWIFT and THz Electronics programs and is based on sub 50 nm Indium Arsenide Composite Channel (IACC) transistor technology with a projected maximum oscillation frequency fmax > 1.0 THz. This development and demonstration may bring to life future sub-millimeter-wave and THz applications such as solutions to brown-out problems, ultra-high bandwidth satellite communication cross-links, and future planetary exploration missions.

Sarkozy, S.; Leong, K.; Lai, R.; Leakey, R.; Yoshida, W.; Mei, X.; Lee, J.; Liu, P.-H.; Gorospe, B.; Deal, W. R.

2011-05-01

163

Prediction of the far field noise from wind energy farms  

NASA Astrophysics Data System (ADS)

The basic physical factors involved in making predictions of wind turbine noise and an approach which allows for differences in the machines, the wind energy farm configurations and propagation conditions are reviewed. Example calculations to illustrate the sensitivity of the radiated noise to such variables as machine size, spacing and numbers, and such atmosphere variables as absorption and wind direction are presented. It is found that calculated far field distances to particular sound level contours are greater for lower values of atmospheric absorption, for a larger total number of machines, for additional rows of machines and for more powerful machines. At short and intermediate distances, higher sound pressure levels are calculated for closer machine spacings, for more powerful machines, for longer row lengths and for closer row spacings.

Shepherd, K. P.; Hubbard, H. H.

1986-04-01

164

Improving long-term ENSO prediction by using ``weather'' noise  

NASA Astrophysics Data System (ADS)

The El-Niño/Southern-Oscillation (ENSO) phenomenon dominates interannual climate signals in and around the Tropical Pacific Ocean and affects the atmospheric circulation and air-sea interaction over many parts of the globe. In particular, these effects are significant during ENSO’s extreme phases, El Niño and La Niña, and include large anomalies in rainfall and temperatures. In practice, accurate long-term forecasting of ENSO beyond 6 months remains a challenge for current state-of-the art statistical, as well as dynamical models. Kondrashov et al. (2005) developed an Empirical Model Reduction (EMR) model of ENSO based on monthly time series of sea surface temperature (SST) anomalies in a tropical belt spanning the three major ocean basins. EMR is a methodology for constructing stochastic models based on the observed evolution of selected climate fields; these models represent unresolved processes (“weather” noise) as multivariate, spatially correlated stochastic forcing. In EMR, multiple polynomial regression is used to estimate the nonlinear, deterministic propagator of the dynamics, as well as multi-level additive stochastic forcing directly from the SST dataset. The EMR-ENSO model has competitive forecast capabilities, which are due to its nonlinear dynamical operator’s ability to capture ENSO’s leading quasi-quadrennial and quasi-biennial oscillatory modes of low-frequency variability (LFV). We demonstrate here a new method for improving LFV forecasting based on estimating the path of the weather noise by an EMR-ENSO model. The method (i) selects samples --- or ``snippets" --- of the noise from past LFV phases that resemble the one occurring at the start of the forecast; and (ii) based on this selection, uses appropriate noise snippets to force the model into the future. The domain of validity of this procedure depends on the nature of the model's pathwise response to noise perturbations; it is shown numerically that the EMR-ENSO model's response to such perturbations is linear on interannual time scales. In the cross-validated hindcast experiments, the method exhibits significantly better prediction skill at 6--16 months lead time for the Niño-3 index and the global SST field, when compared with standard EMR-ENSO model prediction based on a large ensemble of arbitrary realizations of the weather noise.

Kondrashov, D. A.; Chekroun, M.; Ghil, M.

2010-12-01

165

Modeling for Airframe Noise Prediction Using Vortex Methods  

NASA Astrophysics Data System (ADS)

Various components of the airframe are known to be a significant source of noise. With the advent of technology in quieting modern engines, airframe generated noise competes and, in certain instances, surpasses the engine noise. Airframe noise is most pronounced during aircraft approach when the engines are operating at reduced thrust, and airframe components such as high-lift devices and landing gears are in deployed conditions. Recent experimental studies have reaffirmed that the most significant sources of high-lift noise are from the leading-edge slat and the side edges of flaps. Studies of flow field around these structures have consistently shown that there are complicated unsteady vortical flows such as vortex shedding, secondary vortices and vortex breakdown, which are susceptible to far-field radiated sound. The near-field CFD computational data have been used to calculate the far-field acoustics by employing Ffowcs-Williams/Hawkings equation using Lighthill's analogy. However, because of the limit of current computing capacity, it is very time consuming to generate unsteady Navier-Stokes (N-S) computational data for aeroacoustics. Although the N-S simulations are probably necessary to reveal many complex flow phenomena that are unsteady and fully nonlinear, these simulations are not feasible to be used for parametric design. purposes. The objective of this study is thus to develop theoretical models for airframe noise predictions which have quick turn-around computing time. Since it is known that vorticity is a major mechanism responsible for noise generation on high-lift devices, vortex methods have been chosen as modeling tools. Vortex methods are much faster in comparison with other numerical methods, yet they are able to incorporate nonlinear interactions between vortices. Obviously, as with any theoretical model, assumptions have to be made and justified when such models are used in complex flow. The merit and applicability of the models for aeroacoustics applications will be investigated. Issues related with conservation of vorticity, unsteady Kutta conditions and nonlinear frequency response to vortex shedding will be addressed.

Zheng, Z. Charlie

2002-12-01

166

Measurements and predictions of turboprop noise at high cruise speed  

NASA Astrophysics Data System (ADS)

Acoustic tests of advanced turboprop (Prop-Fan) models have taken place in or on three facilities: an acoustic wind tunnel, an aerodynamic wind tunnel, and a flight vehicle. Comparisons of data from the three facilities are made for two model designs, the unswept SR-2 and the swept SR-3. The importance of noise propagation through the boundary layer to microphones mounted on the surface of a flight vehicle is discussed and limited comparisons between predictions and measurements are shown. It is concluded that existing methodology is adequate for predictions at high cruise Mach number and that further development is required to improve the methodology for predicting fuselage and wind tunnel boundary layer propagation effects.

Metzger, F. B.

1983-04-01

167

Evaluation of three models used for predicting noise propagated long distances overground  

Microsoft Academic Search

Pershing 2 missile elimination noise measurements were used as the basis for comparing three noise prediction programs' ground-to-ground propagation modeling approaches. The effects of atmospheric refraction, atmospheric absorption, and ground impedance are considered. The noise models were compared because they are currently in use, in different venues, for environmental noise propagation modeling. The respective strong points of each model are

W. R. Lundberg

1991-01-01

168

Supersonic jet noise - Its generation, prediction and effects on people and structures  

Microsoft Academic Search

This paper presents the results of a study aimed at quantifying the effects of jet source noise reduction, increases in aircraft lift, and reduced aircraft thrust on the take-off noise associated with supersonic civil transports. Supersonic jet noise sources are first described, and their frequency and directivity dependence are defined. The study utilizes NASA's Aircraft Noise Prediction Program in a

J. S. Preisser; R. A. Golub; J. M. Seiner; C. A. Powell

1990-01-01

169

V\\/STOL rotary propulsor noise prediction model update and evaluation  

Microsoft Academic Search

A literature review was conducted to identify and evaluate high quality noise measurements of propeller, variable pitch fan, fixed pitch fan, helicopter, lift fan, core engine, and jet noise for the preparation of a data base with emphasis on recent measurements of in-flight propulsors. The effects of forward flight on V\\/STOL propulsor noise were evaluated and the noise prediction model

B. Magliozzi

1979-01-01

170

Formulas for Predicting Audible Noise from Overhead High Voltage AC and DC Lines  

Microsoft Academic Search

This paper describes Bonneville Power Administration's basic philosophy for predicting audible noise from ac and dc high voltage transmission lines. General formulas for predicting the A-weighted audible noise during rain for ac lines and during fair weather for dc lines which were developed from data from full-scale lines are presented. From this basic calculation, audible noise cumulative distributions, frequency spectrums,

V. L. Chartier; R. D. Stearns

1981-01-01

171

Predictability of the coherent-noise model and its applications.  

PubMed

We study the threshold distribution function of the coherent-noise model for the case of infinite number of agents. This function is piecewise constant with a finite number of steps n. The latter exhibits a 1/f behavior as a function of the order of occurrence of an avalanche and hence versus natural time. An analytic expression of the expectation value E(S) for the size S of the next avalanche is obtained and used for the prediction of the next avalanche. Apart from E(S), the number of steps n can also serve for this purpose. This enables the construction of a similar prediction scheme which can be applied to real earthquake aftershock data. PMID:23004732

Sarlis, N V; Christopoulos, S-R G

2012-05-25

172

Prediction of acoustic scattering in the time domain and its applications to rotorcraft noise  

NASA Astrophysics Data System (ADS)

This work aims at the development of a numerical method for the analysis of acoustic scattering in the time domain and its applications to rotorcraft noise. This purpose is achieved by developing two independent methods: (1) an analytical formulation of the pressure gradient for an arbitrary moving source and (2) a time-domain moving equivalent source method. First, the analytical formulation for the pressure gradient is developed to fulfill the boundary condition on a scattering surface to account for arbitrary moving incident sources. A semi-analytical formulation was derived from the gradient of the Ffowcs Williams-Hawkings (FW-H) equation. This formulation needs to calculate the observer time differentiation outside the integrals numerically. A numerical algorithm is developed to implement this formulation in an aeroacoustic prediction code. A new analytical formulation is presented in the thesis. In this formulation, the time differentiation is taken inside the integrals analytically. This formulation avoids the numerical time differentiation with respect to the observer time, which is computationally more efficient. The acoustic pressure gradient predicted by these two formulations is validated through comparison with available exact solutions for a stationary and moving monopole sources. The agreement between the predictions and exact solutions is excellent. One of the advantages of this analytic formulation is that it efficiently provides the boundary condition for the acoustic scattering of sound generated from an arbitrary moving source, such as rotating blades, which undergoes rotation, flapping and lead-lag motions. The formulation is applied to the rotor noise problems for two model rotors (UH-1H and HART-I). For HART-I rotor, CFD/CSD coupling was used to provide unsteady aerodynamics and trim solutions of the blade motion. A purely numerical approach is compared with the analytical formulations. The agreement between the analytical formulations and the numerical method is excellent for both stationary and moving observer cases. The formulation for the pressure gradient is first used to predict acoustic scattering in the frequency domain. The prediction is validated with the exact solution for acoustic scattering generated by a monopole source by a stationary sphere. A Bo105 helicopter and a notional heavy lift quad tilt rotor are considered to demonstrate a potential significance of acoustic scattering of rotorcraft noise. NASA's Fast Scattering Code is used for the frequency-domain scattering solver. Secondly, a new and efficient time domain acoustic scattering method using a moving equivalent source is developed to predict acoustic scattering in the time domain efficiently. The time-domain method provides entire frequency solutions in a single computation and is able to predict acoustic scattering of aperiodic signals. The method assumes an acoustically rigid surface for a scattering body and neglects the refraction effect by non-uniform flow around the scattering body. The pressure-gradient boundary condition is determined on a scattering surface and then the scattered field is calculated by using equivalent sources located within the scattering surface. Linear shape functions are used to discretize the strength of the equivalent sources in time and singular value decomposition is used to overcome potential numerical instability. The detailed numerical algorithm is addressed in the thesis. The method is more efficient numerically and easier to implement than other time-domain methods using a finite difference scheme or boundary integral equations because it is not necessary to find the solution in the entire domain, it uses a fewer number of equivalent sources than the surface mesh points, and it does not involve surface integrals. The method is validated against exact solutions for various cases including a single frequency monopole source, a dipole source, multiple sources, beat, and broadband noise sources. The predictions are found to be in excellent agreement with the exact solutions. The effect of

Lee, Seongkyu

173

Modeling for Airframe Noise Prediction Using Vortex Methods  

Microsoft Academic Search

Various components of the airframe are known to be a significant source of noise. With the advent of technology in quieting modern engines, airframe generated noise competes and, in certain instances, surpasses the engine noise. Airframe noise is most pronounced during aircraft approach when the engines are operating at reduced thrust, and airframe components such as high-lift devices and landing

Z. Charlie Zheng

2002-01-01

174

Numerical method for predicting ship propeller cavitation noise  

Microsoft Academic Search

During ship travels in high-velocity, propeller cavitation noise predominates in the radiated noise sources. However, experiential data regress method was use to predicate propeller cavitation noise in the past. In this article, propeller cavitation noise has been calculated by numerical computation method. From the engineering point of view, ship propeller has been disposed as a dipole bubble. Bubble volume pulse

Yong-Kun Zhang; Ying Xiong

2011-01-01

175

STUDY OF VEHICULAR TRAFFIC NOISE AND ITS PREDICTION  

Microsoft Academic Search

ABSTRACT The major contribution of the traffic noise, towards overall noise pollution scenario, is awell,known ,established fact. Traffic noise from ,highways ,creates problems ,for surrounding areas, especially when there are high traffic volumes and high speeds. Vehicular traffic noise problem as contributed by various kinds of vehicles like heavy, medium trucks\\/buses, automobiles and two wheelers. Many western countries have

NAROTAM KUMAR; PARAS KUMAR

176

'Integral Noise': An automatic calculation model for the prediction and control of fixed-wing aircraft noise. I - General considerations, theoretical bases and model analysis  

NASA Astrophysics Data System (ADS)

A description is given of the INTNOI Integral Noise Program for advanced aircraft noise prediction and control. This computer model performs, on a modular basis, the analysis of both boundary layer aerodynamic noise and engine noise for the case of such turbofan-powered commercial aircraft as the 737. It also permits the prediction of noise levels due to engine and aerodynamic sources in the communities affected by approach and landing noise footprints. Attention is given to the effect on engine noise levels of low and high fan bypass ratios, the noise components contributed by nacelles, slats, and flaps at various angles, and the specialized options offered by the modular-structure program.

Bossa, F.; Gualdi, R.

1981-10-01

177

Prediction of BVI noise patterns and correlation with wake interaction locations  

Microsoft Academic Search

High resolution fluctuating airloads data were acquired during a test of a contemporary design United Technologies model rotor in the Duits-Nederlandse Windtunnel (DNW). The airloads are used as input to the noise prediction program WOPWOP, in order to predict the blade-vortex interaction (BVI) noise field on a large plane below the rotor. Trends of predicted advancing and retreating side BVI

Michael A. Marcolini; Ruth M. Martin; Peter F. Lorber; T. A. Egolf

1992-01-01

178

Estimation of the far-field directivity of broadband aeroengine fan noise using an in-duct axial microphone array  

Microsoft Academic Search

This paper presents a measurement technique for estimating the far-field directivity of the sound radiated from a duct using measurements of acoustic pressure made inside the duct. The technique is restricted to broadband, multi-mode sound fields whose directivity patterns are axi-symmetric, and whose modes are mutually uncorrelated. The technique uses a transfer function to relate the output from an in-duct

C. R. Lowis; P. F. Joseph; A. J. Kempton

2010-01-01

179

Program for Helicopter Gearbox Noise Prediction and Reduction.  

National Technical Information Service (NTIS)

A method of computing helicopter gearbox noise from design and operating data is verified by a comparison of calculated and measured gearbox noise spectra. Measurements on CH-47 helicopters are used to provide experimental data. Positive identification of...

I. Laskin R. A. Badgley

1970-01-01

180

Characteristics and prediction of magnetic noise due to DC electric railcars for biomagnetic measurements  

Microsoft Academic Search

A magnetically shielded room for biomagnetism should be designed taking account of the S\\/N ratio of the biomagnetic signal to the environmental magnetic noise generated mainly by dc electric railcars at an installed location. This paper describes the characteristics of the fluctuation of magnetic noise and a method of prediction of its amplitude. The distance dependence of the magnetic noise

Keita Yamazaki; Kazuo Kato; Koichiro Kobayashi; Yoshinori Uchikawa; Yoji Kumagai; Akira Haga; Koji Fujiwara

2001-01-01

181

Vowel and consonant confusion in noise by cochlear implant subjects: predicting performance using signal processing techniques  

Microsoft Academic Search

Cochlear implants are able to restore some degree of hearing to deafened individuals; however implant users are particularly susceptible to background noise. The effect of noise can be assessed using vowel and consonant confusions measured in listening experiments. The paper presents three signal processing methods developed to predict patterns in vowel and consonant confusion in noise for cochlear implant users.

Jeremiah J. Remus; Leslie M. Collins

2004-01-01

182

Development of Computational Aeroacoustics Code for Jet Noise and Flow Prediction  

Microsoft Academic Search

Accurate prediction of jet fan and exhaust plume flow and noise generation and propagation is very important in developing advanced aircraft engines that will pass current and future noise regulations. In jet fan flows as well as exhaust plumes, two major sources of noise are present: large-scale, coherent instabilities and small-scale turbulent eddies. In previous work for the NASA Glenn

Theo G. Keith Jr.; Duane R. Hixon

2002-01-01

183

Applications of aero-acoustics to wind turbine noise prediction and control  

NASA Astrophysics Data System (ADS)

Wind turbine noise generation mechanisms are essentially equivalent to the aero-acoustic mechanisms of other rotors, which have been studied in depth for many years. Basic sources for the wind turbine noise radiation process are defined, and their significance assessed. From the analysis, areas of potential improvement in wind turbine noise prediction are defined. Suggestions are made for approaches to wind turbine noise control which separate the noise problems at cut-in from those at rated power. Some of these offer the possibility of noise reduction without unfavourable effects on performance.

Lowson, Martin V.

1993-01-01

184

On the prediction of impact noise, IV: Estimation of noise energy radiated by impact excitation of a structure  

Microsoft Academic Search

This series of papers [1-3] sets out to provide a practical method of predicting the noise radiated by a machinery-type structure as a result of an impact upon it. As such noise energy may vary from 10-8 to 10-3 of the mechanical energy used in the machine, it is necessary to validate the accuracy of the ``energy accountancy equation'' which

J. M. Cuschieri; E. J. Richards

1983-01-01

185

Prediction of mechanical properties of the human calcaneus by broadband ultrasonic attenuation  

Microsoft Academic Search

Broadband ultrasonic attenuation (dB MHz cm?1, nBUA) was determined for specimens from 20 human calcanei, along with apparent density, elasticity (Young's modulus), and compressive strength. The calcanei were modified to provide “whole” (only soft tissue removed), “core” (mediolateral cores corresponding to in vivo measurement region), “can” (cortical end plates removed from core), and “der” (core defatted) samples. The nBUA values

C. M. Langton; C. F. Njeh; R. Hodgskinson; J. D. Currey

1996-01-01

186

Noise Localization after Unilateral Attenuation.  

National Technical Information Service (NTIS)

Partial hearing loss was simulated by insertion of V51-R plastic ear plugs. Subjects wore plugs continuously for periods ranging from six hours to three days. Predictable shifts in localization errors were observed when the stimulus was a broad-band noise...

R. W. Bauer J. L. Matuzsa R. F. Blackmer S. Glucksberg

1966-01-01

187

Broadband Seismic Background Noise at Temporary Seismic Stations Observed on a Regional Scale in the Southwestern United States  

Microsoft Academic Search

Background noise power spectral density (PSD) estimates for 54 PASS- CAL Colorado Plateau\\/Rio Grande Rift\\/Great Plains Seismic Transect (LA RISTRA) stations were computed using data from 1999 to 2000. At long periods (0.01-0.1 Hz), typical vertical noise levels are approximately 12 dB higher than the nearby Global Seismic Network (GSN) borehole station ANMO, but horizontal power spec- tral density (PSD)

David Wilson; Joseph Leon; Richard Aster; James Ni; John Schlue; Steve Grand; Steve Semken; Scott Baldridge; Wei Gao

2002-01-01

188

Prediction and Control of Rail Transit Noise and Vibration - A State-of-the-Art Assessment.  

National Technical Information Service (NTIS)

The report contains results of a review of current technology for the prediction and control of urban rail transit noise and vibration, with primary emphasis on the parameters affecting propagation paths. Included are tools for the prediction of wayside n...

J. E. Manning J. J. Fredberg R. G. Cann

1974-01-01

189

Simplified contact filters in wheel/rail noise prediction  

NASA Astrophysics Data System (ADS)

When predicting rolling noise due to wheel and rail roughness a “contact filter” is generally applied to account for the effect of the finite size of the wheel/rail contact. For time-domain analysis these calculations must be fast enough to get results in a reasonable time. Remington and Webb have devised a versatile three-dimensional ‘distributed point reacting spring’ (DPRS) contact model that is relatively quick, but if only one line of data is available along the contact it is unnecessarily complex, so a simpler two-dimensional version has been developed here. When this new model was checked against a Boussinesq analysis of the contact, the results in one-third octave bands were found to agree to within 3 dB. These results further suggest that the two-dimensional DPRS model might have an unexpectedly wide range of applicability, including large amplitude sinusoidal roughness and discrete features such as a rail joint. When implemented at each step in a time-domain wheel/rail interaction analysis, this model gave similar results to quasi-static roughness filtering with a constant load for moderate roughness, but dynamic effects became significant when the roughness amplitudes were large, particularly with dipped rail joints.

Ford, R. A. J.; Thompson, D. J.

2006-06-01

190

Image discrimination models predict detection in fixed but not random noise.  

PubMed

By means of a two-interval forced-choice procedure, contrast detection thresholds for an aircraft positioned on a simulated airport runway scene were measured with fixed and random white-noise masks. The term fixed noise refers to a constant, or unchanging, noise pattern for each stimulus presentation. The random noise was either the same or different in the two intervals. Contrary to simple image discrimination model predictions, the same random noise condition produced greater masking than the fixed noise. This suggests that observers seem unable to hold a new noisy image for comparison. Also, performance appeared limited by internal process variability rather than by external noise variability, since similar masking was obtained for both random noise types. PMID:9291614

Ahumada, A J; Beard, B L

1997-09-01

191

Jet Engine Noise Generation, Prediction and Control, Chapter 86.  

National Technical Information Service (NTIS)

Aircraft noise has been a problem near airports for many years. It is a quality of life issue that impacts millions of people around the world. Solving this problem has been the principal goal of noise reduction research that began when commercial jet tra...

D. L. Huff E. Envia

2004-01-01

192

Prediction of the interaction noise emitted by helicopter fenestrons  

Microsoft Academic Search

This paper is concerned with the sound generation from a helicopter fenestron due to rotor-stator interactions. Two mechanisms are investigated: (1) the rotor noise due to potential disturbances created by the cylindric struts (transmission shaft and support arm) located behind the rotorplane, and (2) the stator noise resulting from the interaction with the rotor viscous wakes. Each mechanism is theoretically

Francette Fournier; Michel Roger

1989-01-01

193

Numerical Prediction of Laminar Instability Noise for NACA 0012 Aerofoil  

Microsoft Academic Search

Aerofoil self-generated noise is recognized to be of fundamental importance in the frame of applied aeroacoustics and the use of computational methods to assess the acoustic behaviour of airframe components challenges an even larger community of engineers and scientists. Several noise generation mechanisms can be found which are mainly related to the physical development of turbulence over the boundary layer.

Michele de Gennaro; Andreas Hueppe; Helmut Kuehnelt; Manfred Kaltenbacher

2011-01-01

194

Continuum emission and broadband electrostatic noise at the low latitude boundary layer: A diagnostic of boundary layer dynamics  

NASA Astrophysics Data System (ADS)

We examine the plasma and radio waves near the inner edge of the low latitude boundary layer (LLBL) during a period of time when the layer is in a ``pulsed'' oscillating configuration. Previous work suggests there are numerous possible explanations for such oscillations including a Kelvin-Helmholtz instability, flux transfer events, and a boundary response to solar wind pressure oscillations. We demonstrate that the inner edge of the LLBL is indeed in motion, based upon the influence this motion has on the incident freely-propagating continuum emission. We also demonstrate that the inner boundary contains impulsive broadband events that appear, in high resolution, as a series of bipolar solitary pulses. These are the result of a kinetic electron beam instability occurring in association with the boundary fluid motion. We suggest that the large-scale fluid motion drives the kinetic instability via particle evacuation near the oscillating boundary.

Farrell, W. M.; Fitzenreiter, R. J.; Kaiser, M. L.; Goetz, K.; Maksimovic, M.; Reiner, M. J.

2002-06-01

195

Evaluation of three models used for predicting noise propagated long distances overground  

NASA Astrophysics Data System (ADS)

Pershing 2 missile elimination noise measurements were used as the basis for comparing three noise prediction programs' ground-to-ground propagation modeling approaches. The effects of atmospheric refraction, atmospheric absorption, and ground impedance are considered. The noise models were compared because they are currently in use, in different venues, for environmental noise propagation modeling. The respective strong points of each model are emphasized. The results are used to delineate the needs for development of a model which produces both rapid and physically detailed predictions.

Lundberg, W. R.

1991-09-01

196

Peculiarities of Human Sleep under Conditions of Continuous Prolonged Influence of Broad-Band Noise of Average Intensity.  

National Technical Information Service (NTIS)

Studies were conducted at the Prof. F. D. Garbov laboratory on the effects of continuous protracted broad band noise on sleep and on the transitional state between sleep and wakefulness to determine the physiological basis for the disturbing effects of no...

V. I. Myasnikov O. P. Kozerenko I. Y. Yakovleva E. I. Matsnev I. P. Lebedeva

1969-01-01

197

Prediction of BVI noise patterns and correlation with wake interaction locations  

NASA Astrophysics Data System (ADS)

High resolution fluctuating airloads data were acquired during a test of a contemporary design United Technologies model rotor in the Duits-Nederlandse Windtunnel (DNW). The airloads are used as input to the noise prediction program WOPWOP, in order to predict the blade-vortex interaction (BVI) noise field on a large plane below the rotor. Trends of predicted advancing and retreating side BVI noise levels and directionality as functions of flight condition are presented. The measured airloads have been analyzed to determine the BVI locations on the blade surface, and are used to interpret the predicted BVI noise radiation patterns. Predicted BVI locations are obtained using the free wake model in CAMRAD/JA, the UTRC Generalized Forward Flight Distorted Wake Model, and the UTRC FREEWAKE analysis. These predicted BVI locations are compared with those obtained from the measured pressure data.

Marcolini, Michael A.; Martin, Ruth M.; Lorber, Peter F.; Egolf, T. A.

198

“Buzz-saw” noise: Prediction of the rotor-alone pressure field  

NASA Astrophysics Data System (ADS)

Public expectations of lower environmental noise levels, and increasingly stringent legislative limits on aircraft noise, result in noise being a critical technical issue in the development of jet engines. Noise at take-off, when the engines are at high-power operating conditions, is a key reference level for engine noise certification. “Buzz-saw” noise is the dominant fan tone noise from modern high-bypass-ratio turbofan aircraft engines during take-off. Rotor-alone tones are the key component of buzz-saw noise. The rotor-alone pressure field is cut-off at subsonic fan tip speeds; buzz-saw noise is associated with supersonic fan tip speeds, or equivalently, high power engine operating conditions. A recent series of papers has described new work concerning the prediction of buzz-saw noise. The prediction method is based on modelling the nonlinear propagation of one-dimensional sawtooth waveforms. A sawtooth waveform is a simplified representation of the rotor-alone pressure field. Previous validation of the prediction method focussed entirely on reproducing the spectral characteristics of buzz-saw noise; this was dictated at that time by the availability of spectral data only for comparison between measurement and prediction. In this paper, full validation of the method by comparing measurement and prediction of the rotor-alone pressure field is published for the first time. It is shown that results from the modelling based on a one-dimensional sawtooth waveform capture the essential features of the rotor-alone pressure field as it propagates upstream inside a hard-walled inlet duct. This verifies that predictions of the buzz-saw noise spectrum, which are in good agreement with the measured data, are based on a model which reproduces the key physics of the noise generation process. Validation results for the rotor-alone pressure field in an acoustically lined inlet duct are also shown. Comparisons of the measured and predicted rotor-alone pressure field are more difficult to interpret because the acoustic lining significantly modifies the sawtooth waveform, but there remains good agreement with the measured spectral data. The buzz-saw noise prediction code used to generate the simulations in this paper has been used by the Rolls-Royce Noise Department since 2004.

McAlpine, A.; Schwaller, P. J. G.; Fisher, M. J.; Tester, B. J.

2012-10-01

199

Prediction Model for Noise from Low-Altitude Military Aircraft.  

National Technical Information Service (NTIS)

For a number of years, the National Physical Laboratory, supported by the Ministry of Defense, has been developing AIRNOISE, a mathematical model for computing aircraft noise contours. As part of the continuous programme of development of the model we wer...

B. F. Berry J. D. Speakman

1993-01-01

200

Broad-band low-noise preamplifier design with GaAs MESFETs for optical communication systems  

Microsoft Academic Search

Classical designs of transimpedance preamplifiers for optical receiver circuits use common-emitter (C-E) or common-source (C-S) input stages. The use of current-mode techniques to design photoreceivers for optical communication systems has been shown to offer significant bandwidth advantages over traditional voltage-mode designs. In this paper, we focus on the design of a wide-band, low-noise photoreceiver in GaAs using current-based amplifying techniques.

A. B. Bende; Bozena Kaminska

1998-01-01

201

Order from chaos? 1\\/ f noise predicts performance on reaction time measures  

Microsoft Academic Search

In repetitive tasks, latencies typically display non-random variation called 1\\/f noise, but the magnitude of 1\\/f noise can depend on effort. Between-participant variation in 1\\/f noise might therefore predict differences in performance for tasks that are sensitive to effort. Feedback was manipulated to suggest that participants had (or had not) shown bias on a preliminary task. Participants then completed a

Joshua Correll

2011-01-01

202

The prediction of aerodynamic and wheel\\/rail noise generated by high-speed trains  

Microsoft Academic Search

Wheel\\/rail interactions and aerodynamic fluctuations are the important sources of wayside noise produced by high-speed railway trains. The dominance of one or the other of these sources depends entirely on the relative effectivenss of each in generating radiated noise. Equations are given for the calculation of both the wheel\\/rail and aerodynamic noise levels and their predictions are compared to peak

W. F. King III

1977-01-01

203

“Buzz-saw” noise: A comparison of modal measurements with an improved prediction method  

Microsoft Academic Search

“Buzz-saw” noise is radiated from a turbofan inlet duct when the fan tip speed is supersonic. In a recent article the effect of an acoustic liner on buzz-saw noise has been examined. Spectral measurements in a rigid and an acoustically lined inlet duct have been compared. Also these measurements have been utilized to assess a buzz-saw noise prediction method. The

A. McAlpine; M. J. Fisher; B. J. Tester

2007-01-01

204

``Buzz-saw'' noise: A comparison of modal measurements with an improved prediction method  

Microsoft Academic Search

``Buzz-saw'' noise is radiated from a turbofan inlet duct when the fan tip speed is supersonic. In a recent article the effect of an acoustic liner on buzz-saw noise has been examined. Spectral measurements in a rigid and an acoustically lined inlet duct have been compared. Also these measurements have been utilized to assess a buzz-saw noise prediction method. The

A. McAlpine; M. J. Fisher; B. J. Tester

2007-01-01

205

Ocean acoustic noise and passive coherent array processing  

Microsoft Academic Search

Broadband correlation processing for extracting time-domain Green's functions and coherent wavefronts from random ocean noise has been demonstrated recently using experiments and numerical simulations that are consistent with theoretical predictions. Ocean acoustic noise processing presents additional challenges over its seismological counterpart. Mainly, the ocean environment is temporally non-stationary and it is spatially heterogeneous. Further, in the lower underwater acoustic frequency

Philippe Roux; W. A. Kuperman; Karim G. Sabra

2011-01-01

206

Prediction of noise radiation from basic configurations of landing gears by means of computational aeroacoustics  

Microsoft Academic Search

Noise radiation from aircraft during the takeoff and landing has become a major issue for inhabitants living in the vicinity of airports and thus for regulation authorities and aircraft developers. However the numerical simulation of aeroacoustic noise, especially for complex geometries like a landing gear, remains one of the most difficult challenges in aeroacoustics. The present study, aiming at predicting

Peter Drage; Bruno Wiesler; Pieter van Beek; Leonard van Lier; Rene Parchen; Peter Tibaut

2007-01-01

207

Prediction of potential noise interactions in axial-flow machines - Application to the helicopter fenestron  

Microsoft Academic Search

A method for predicting the far-field noise created in a rotor by the flow around cylindrical obstacles (such as support arms) placed downstream of the rotor is proposed. Application of the method to helicopter rotor blades shows that this noise source can account for the fundamental and first harmonics of the blade frequencies. It is suggested that higher frequences may

Francette Fournier; Michel Roger

1989-01-01

208

Millimeter-wave antenna noise temperature due to rain clouds: Theoretical model and statistical prediction  

Microsoft Academic Search

Model-oriented methods to predict antenna noise temperature due to rainfall along slant paths are developed and illustrated for communication systems at Ka band and above. The adopted sky noise Eddington model (SNEM) relies on an accurate analytical solution of the radiative transfer equation and on stratiform and convective rainfall stratified structures, synthetically generated from cloud-resolving model statistics. The approach to

Frank Silvio Marzano; Mario Montopoli

2009-01-01

209

Comparison of frequency domain noise reduction strategies based on multichannel Wiener filtering and spatial prediction  

Microsoft Academic Search

In this paper two multichannel noise reduction strategies are compared in the context of binaural hearing aids. Recently a novel noise reduction method based on spatial-temporal prediction (STP) was introduced which showed an improvement over methods based on multichannel Wiener filtering, although at the cost of a higher computational complexity. Whereas this newmethod operates in the time domain, hearing aids

Bram Cornelis; Marc Moonen; Jan Wouters

2009-01-01

210

Quantifying the effects of dynamical noise on the predictability of a simple ecosystem model  

Microsoft Academic Search

SUMMARY The need to understand the effects of anthropogenic perturbations on ocean biology has renewed interest in ecosystem and biogeochemical models in recent years. We develop a nonlinear time series approach to quantify the effects of different types of noise on ecosystem dynamics. Different types of noise can alter the local predictability of the system, induce qualitative regime shifts in

Barbara A. Bailey; Scott C. Doney; Ivan D. Lima

2004-01-01

211

Noise prediction of rotor-stator interaction for fan\\/compressor  

Microsoft Academic Search

A method for predicting the noise generated by rotor wake-stator interaction is presented by solving the generalized Lighthill equation. First, a wake model behind the rotor blades is given. Then, the unsteady forces on the stator blades can be computed, using a two-dimensional compressible unsteady computation method. The rotor stator interaction noise is then obtained, considering the effects of the

Xiaofeng Sun; Zongan Hu; Shen Zhou

1989-01-01

212

SR3 prop fan noise prediction based on time domain method  

Microsoft Academic Search

This paper presents a numerical technique for the prediction of the noise of SR-3 prop-fan. The blades upper and lower surfaces are described by a helical coordinate system which also used to divide blade surfaces into panels. Two different acoustic formulation in the time domain are used to improve the speed and the efficiency of the noise calculation: Woan and

Yong S. Kim; Oh H. Rho

1990-01-01

213

NUMERICAL PREDICTION OF AEROENGINE FAN STAGE TONE NOISE SOURCES USING CFD  

Microsoft Academic Search

This paper examines the extent to which 'conventional' low order accurate CFD codes can be applied to prediction of fan stage tone noise sources. Each of the major tone noise sources is consid ered in turn, with representative grid sizes estimated using assumptions about the capability of such codes. Simplifying approximations are also considered where they allow the more efficient

Alexander G. Wilson; John Coupland

214

Data analysis and noise prediction for the QF1B experimental fan stage  

Microsoft Academic Search

The results of a fan noise data analysis and prediction effort using experimental data obtained from tests on the QF-1B research fan are described. Surface pressure measurements were made with flush mounted sensors installed on selected rotor blades and stator vanes and noise measurements were made by microphones located at the far field. Power spectral density analysis, time history studies,

D. B. Bliss; K. L. Chandiramani; A. G. Piersol

1976-01-01

215

In-Vehicle Tire Sound Quality Prediction from Tire Noise Data  

Microsoft Academic Search

Tire Sound Quality is an increasingly important factor for customer satisfaction within the replacement tire market. Manufacturers who compete in this market must be capable of predicting a driver's perception of tire noise as early in the design process as possible in order to reduce development time and cost. Typical methods for tire noise evaluation each have limitations that require

Eric C. Frank; D. J. Pickering; Chris Raglin; Cooper Tire

216

Noise Estimation Using Mean Square Cross Prediction Error for Speech Enhancement  

Microsoft Academic Search

This paper shows the feasibility of noise extraction from noisy speech and presents a two-stage approach for speech enhancement. The preproposed mean square cross prediction error (MSCPE) based blind source extraction algorithm is utilized to extract the additive noise from the noisy speech signal in the first stage. After that a modified spectral subtraction and a modified Wiener filter approach

Gang Wang; Chunguang Li; Le Dong

2010-01-01

217

Community Noise Exposure Resulting from Aircraft Operations: Application Guide for Predictive Procedure.  

National Technical Information Service (NTIS)

This report is one of a series describing the research program undertaken by the Aerospace Medical Research Laboratory to develop procedures for predicting the community noise exposure resulting from aircraft operations. It discusses the applications of t...

D. E. Bishop

1974-01-01

218

Predicting Antenna Noise Temperature Due to Rain Clouds at Microwave and Millimeter-Wave Frequencies  

Microsoft Academic Search

Model-oriented methods to predict antenna noise temperature due to rainfall along slant paths are developed and illustrated for communication systems at Ka-band and above. The adopted Sky Noise Eddington Model (SNEM) relies on an accurate analytical solution of the radiative transfer equation and on stratiform and convective rainfall stratified structures, synthetically generated from cloud-resolving model statistics. The approach to predict

Frank S. Marzano

2007-01-01

219

A rail noise prediction model for the Tehran–Karaj commuter train  

Microsoft Academic Search

Rail noise prediction models enable consideration of different scenarios for the optimal management of noise prevention and mitigation. This project is aimed at developing an equation that enables computation of LA,max for the Tehran–Karaj commuter train, a type of Diesel–Electric Locomotive. The form of the proposed model is derived from equations for predicting LA,max for a single locomotive pass-by, proposed

P. Nassiri; M. Abbaspour; M. Mahmoodi; Sh. Givargis

2007-01-01

220

Electrochemical Noise Resistance as a Tool for Corrosion Rate Prediction  

Microsoft Academic Search

Current and potential fluctuations (electrochemical noise [EN]) between two nominally identical carbon steel electrodes were recorded in a solution of sodium phosphate (NaâPOâ) at different concentrations. After passivation was reached, pitting was induced by addition of chlorides. Data were collected with different sampling rates. Linear polarization resistances (LPR) also were measured. Electrochemical signals were transposed in the frequency domains using

G. Gusmano; S. Pacetti; A. DAmico; A. Petitti; G. Montesperelli

1997-01-01

221

Accuracy of aircraft noise exposure calculations and predictions  

SciTech Connect

There are many noise exposures measures in use for rating the effects of aircraft fly over noise. Almost all, if not all, of these measures are of a logarithmic type with decibel like units. Basically all measures take into account both the number of flights heard as well as the average of the weighted single event noise levels. In general this is realized by computing or measuring the sound intensity averaged on an energy basis and multiplying this average by a function of the number of events. Of the thus found quantity, which we will call the linear measure the logarithm is then taken and apart from constants, this gives the sought for noise exposure measure, called the logarighmic measure. The two basic quantities, the number of events and the average of the sound intensity of the heard events are, both functions of many stochastic factors. The measures, both the linear one and the logarithmic one, are therefore also stochastic variables, that can be described by a probability function.

Peutz, V.M.A.

1982-01-01

222

Evidence for a change in the radiation mechanism in the hard state of GRO J1655-40. Hysteresis in the broad-band noise components  

NASA Astrophysics Data System (ADS)

We have analysed archival data from the Rossi X-ray Timing Explorer (RXTE) to study the aperiodic variability of the black hole binary GRO J1655-40 during the hard state of the 2005 outburst. This work was motivated by the recent finding of a spectral change in the hard state X-ray radiation mechanism in black hole binaries. We computed the 0.008-64 Hz power spectral density during the rise and decay of the 2005 outburst, and we found that they were reasonably well modelled by the sum of two, broad Lorenztian functions in most cases (plus a narrow QPO), which correspond to three different variability components. Our aim is to study the evolution of the timing properties of the source during the outburst, by studying the correlation between the characteristics of the broad-band noise components in the power spectra and the source luminosity. Our results suggest that the whole power spectrum shifts to high (low) frequencies as the source luminosity increases (decreases), in agreement with previous studies of other black hole binaries. However, we also detect a strong `hysteresis' pattern in the `frequency-luminosity' plots, and show that the `critical' luminosity limit, above which the timing properties of the source change, is different during the rise and the decay phase of the outburst. We discuss the general implications of these results in the context of the truncated disc model.

Reig, P.; Papadakis, I. E.; Sobolewska, M. A.; Malzac, J.

2013-09-01

223

Evidence for a change in the radiation mechanism in the hard state of GRO J1655-40. Hysteresis in the broad-band noise components  

NASA Astrophysics Data System (ADS)

We have analysed archival data from the Rossi X-ray Timing Explorer (RXTE) to study the aperiodic variability of the black hole binary GRO J1655-40 during the hard state of the 2005 outburst. This work was motivated by the recent finding of a spectral change in the hard state X-ray radiation mechanism in black hole binaries. We computed the 0.008-64 Hz power spectral density during the rise and decay of the 2005 outburst, and we found that they were reasonably well modelled by the sum of two, broad Lorenztian functions in most cases (plus a narrow QPO), which correspond to three different variability components. Our aim is to study the evolution of the timing properties of the source during the outburst, by studying the correlation between the characteristics of the broad-band noise components in the power spectra and the source luminosity. Our results suggest that the whole power spectrum shifts to high (low) frequencies as the source luminosity increases (decreases), in agreement with previous studies of other black hole binaries. However, we also detect a strong `hysteresis' pattern in the `frequency-luminosity' plots, and show that the `critical' luminosity limit, above which the timing properties of the source change, is different during the rise and the decay phase of the outburst. We discuss the general implications of these results in the context of the truncated disc model.

Reig, P.; Papadakis, I. E.; Sobolewska, M. A.; Malzac, J.

2013-11-01

224

Broadband sound absorption by lattices of microperforated cylindrical shells  

NASA Astrophysics Data System (ADS)

Absorption of broadband noise by sonic crystals consisting of microperforated cylindrical shells is proposed and experimentally demonstrated. The theoretical study has been performed in the framework of multiple scattering method, where a model for the T matrix of the microperforated shells has been developed. It has been predicted an extraordinary broadband sound absorption that is explained in terms of the multiple scattering phenomena occurring at the surfaces of the absorptive units--the microperforated panels. Our proposal has been supported by experiments performed on a structure consisting of 3 rows of cylindrical shells 3 meters height.

García-Chocano, Victor M.; Cabrera, Suitberto; Sánchez-Dehesa, José

2012-10-01

225

Analysis of impact/impulse noise for predicting noise induced hearing loss  

NASA Astrophysics Data System (ADS)

Studies indicate that the statistical properties and temporal structure of the sound signal are important in determining the extent of hearing hazard. As part of a pilot study to examine hearing conservation program effectiveness, NIOSH collected noise samples of impact noise sources in an automobile stamping plant, focusing on jobs with peak sound levels (Lpk) of greater than 120 dB. Digital tape recordings of sounds were collected using a Type I Precision Sound Level Meter and microphone connected to a DAT tape recorder. The events were archived and processed as .wav files to extract single events of interest on CD-R media and CD audio media. A preliminary analysis of sample wavelet files was conducted to characterize each event using metrics such as the number of impulses per unit time, the repetition rate or temporal pattern of these impulses, index of peakedness, crest factor, kurtosis, coefficient of kurtosis, rise time, fall time, and peak time. The spectrum, duration, and inverse of duration for each waveform were also computed. Finally, the data were evaluated with the Auditory Hazard Assessment Algorithm (AHAAH). Improvements to data collection for a future study examining different strategies for evaluating industrial noise exposure will be discussed.

Vipperman, Jeffrey S.; Prince, Mary M.; Flamm, Angela M.

2003-04-01

226

Auditory brainstem measures predict reading and speech-in-noise perception in school-aged children  

PubMed Central

Reading and speech-in-noise perception, fundamental aspects of human communication, have been linked to neural indices of auditory brainstem function. However, how these factors interact is currently unclear. Multivariate analysis methods (structural equation modeling) were employed to delineate and quantify the relationships among factors that relate to successful reading and speech-in-noise perception in children. Neural measures of subcortical speech encoding that reflect the utilization of stimulus regularities, differentiation of stop consonants, and robustness of neural synchrony predicted 73% of the variance in reading scores. A different combination of neural measures, specifically, utilization of stimulus regularities, strength of encoding of lower harmonics, and the extent of noise-induced timing delays uniquely predicted 56% of the variance in speech-in-noise perception measures. The neural measures relating to reading and speech-in-noise perception were substantially non-overlapping and resulted in poor fitting models when substituted for each other, thereby suggesting distinct neural signatures for the two skills. When phonological processing and working memory measures were added to the models, brainstem measures still uniquely predicted variance in reading ability and speech-in-noise perception, highlighting the robustness of the relationship between subcortical auditory function and these skills. The current study suggests that objective neural markers may prove valuable in the assessment of reading or speech-in-noise abilities in children.

Hornickel, Jane; Chandrasekaran, Bharath; Zecker, Steve; Kraus, Nina

2010-01-01

227

Prediction of noise levels and annoyance from aircraft run-ups at Vancouver International Airport.  

PubMed

Annoyance complaints resulting from engine run-ups have been increasing at Vancouver International Airport for several years. To assist the Airport in managing run-up noise levels, a prediction tool based on a Green's function parabolic equation (GFPE) model has been consolidated, evaluated, and applied. It was extended to include more realistic atmospheric and ground input parameters. Measurements were made of the noise-radiation characteristics of a CRJ200 jet aircraft. The GFPE model was validated by comparing predictions with results in the literature. A sensitivity analysis showed that predicted levels are relatively insensitive to small variations in geometry and ground impedance, but relatively sensitive to variations in wind speed, atmosphere type, and aircraft heading and power setting. Predicted noise levels were compared with levels measured at noise monitoring terminals. For the four cases for which all input information was available, agreement was within 10 dBA. For events for which some information had to be estimated, predictions were within 20 dBA. The predicted annoyance corresponding to the run-up events considered ranged from 1.8% to 9.5% of people awoken, suggesting that noise complaints can be expected. PMID:17902830

Scherebnyj, Katrina; Hodgson, Murray

2007-10-01

228

“Buzz-saw” noise: A comparison of modal measurements with an improved prediction method  

NASA Astrophysics Data System (ADS)

“Buzz-saw” noise is radiated from a turbofan inlet duct when the fan tip speed is supersonic. In a recent article the effect of an acoustic liner on buzz-saw noise has been examined. Spectral measurements in a rigid and an acoustically lined inlet duct have been compared. Also these measurements have been utilized to assess a buzz-saw noise prediction method. The prediction method is based on a one-dimensional nonlinear propagation model. Sound absorption by an acoustic lining can be included in the model. In this article, the buzz-saw noise prediction method is improved by the inclusion in the modelling of the effect of a boundary layer on absorption of sound in a lined duct. Also, modal measurements from a circumferential microphone array have been examined. These show that the principal source of buzz-saw noise is not always the rotor-alone pressure field. Non-rotor-alone scattered tones can be a significant source of buzz-saw noise at low supersonic fan speeds. The numerical simulations, which only predict the rotor-alone tones, have been re-evaluated in light of these new modal measurements.

McAlpine, A.; Fisher, M. J.; Tester, B. J.

2007-10-01

229

Auditory Brainstem Response to Complex Sounds Predicts Self-Reported Speech-in-Noise Performance  

PubMed Central

Purpose To compare the ability of the auditory brainstem response to complex sounds (cABR) to predict subjective ratings of speech understanding in noise on the Speech, Spatial, and Qualities of Hearing Scale (SSQ; Gatehouse & Noble, 2004) relative to the predictive ability of the Quick Speech-in-Noise test (QuickSIN; Killion, Niquette, Gudmundsen, Revit, & Banerjee, 2004) and pure-tone hearing thresholds. Method Participants included 111 middle- to older-age adults (range= 45–78) with audiometric configurations ranging from normal hearing levels to moderate sensorineural hearing loss. In addition to using audiometric testing, the authors also used such evaluation measures as the QuickSIN, the SSQ, and the cABR. Results Multiple linear regression analysis indicated that the inclusion of brainstem variables in a model with QuickSIN, hearing thresholds, and age accounted for 30% of the variance in the Speech subtest of the SSQ, compared with significantly less variance (19%) when brainstem variables were not included. Conclusion The authors’ results demonstrate the cABR’s efficacy for predicting self-reported speech-in-noise perception difficulties. The fact that the cABR predicts more variance in self-reported speech-in-noise (SIN) perception than either the QuickSIN or hearing thresholds indicates that the cABR provides additional insight into an individual’s ability to hear in background noise. In addition, the findings underscore the link between the cABR and hearing in noise.

Parbery-Clark, Alexandra; White-Schwoch, Travis; Kraus, Nina

2013-01-01

230

New formulas for predicting audible noise from overhead HVAC lines using evolutionary computations  

Microsoft Academic Search

Audible noise (AN) produced by corona discharges from high voltage transmission lines is one of the more important considerations in line design. Therefore, line designers must predetermine the AN using prediction formulas. This paper presents the results of applying evolutionary computation techniques using AN data from lines throughout the world to develop new highly accurate formulas for predicting the A-weighted

Kwang-Ho Yang; Dong-Il Lee; Gi-Hyun Hwang; June-Ho Park; Vernon L. Chartier

2000-01-01

231

Noise prediction of rotor-stator interaction for fan/compressor  

NASA Astrophysics Data System (ADS)

A method for predicting the noise generated by rotor wake-stator interaction is presented by solving the generalized Lighthill equation. First, a wake model behind the rotor blades is given. Then, the unsteady forces on the stator blades can be computed, using a two-dimensional compressible unsteady computation method. The rotor stator interaction noise is then obtained, considering the effects of the compressor tube on the noise fields. The total noise power depends on the following parameters: stagger angle and chord of stator blade, spacing of rotor/stator, Mach number, rotor speed, and wake behind the rotor blades. Some numerical results are given to analyze the effect of the spacing of rotor-stator on the noise radiation. The estimated results show a reasonable agreement with the experimental data.

Sun, Xiaofeng; Hu, Zongan; Zhou, Shen

1989-01-01

232

An instantaneous spatiotemporal model to predict a bicyclist's Black Carbon exposure based on mobile noise measurements  

NASA Astrophysics Data System (ADS)

Several studies have shown that a significant amount of daily air pollution exposure, in particular Black Carbon (BC), is inhaled during trips. Assessing this contribution to exposure remains difficult because on the one hand local air pollution maps lack spatio-temporal resolution, at the other hand direct measurement of particulate matter concentration remains expensive. This paper proposes to use in-traffic noise measurements in combination with geographical and meteorological information for predicting BC exposure during commuting trips. Mobile noise measurements are cheaper and easier to perform than mobile air pollution measurements and can easily be used in participatory sensing campaigns. The uniqueness of the proposed model lies in the choice of noise indicators that goes beyond the traditional overall A-weighted noise level used in previous work. Noise and BC exposures are both related to the traffic intensity but also to traffic speed and traffic dynamics. Inspired by theoretical knowledge on the emission of noise and BC, the low frequency engine related noise and the difference between high frequency and low frequency noise that indicates the traffic speed, are introduced in the model. In addition, it is shown that splitting BC in a local and a background component significantly improves the model. The coefficients of the proposed model are extracted from 200 commuter bicycle trips. The predicted average exposure over a single trip correlates with measurements with a Pearson coefficient of 0.78 using only four parameters: the low frequency noise level, wind speed, the difference between high and low frequency noise and a street canyon index expressing local air pollution dispersion properties.

Dekoninck, Luc; Botteldooren, Dick; Int Panis, Luc

2013-11-01

233

Prediction of potential noise interactions in axial-flow machines - Application to the helicopter fenestron  

NASA Astrophysics Data System (ADS)

A method for predicting the far-field noise created in a rotor by the flow around cylindrical obstacles (such as support arms) placed downstream of the rotor is proposed. Application of the method to helicopter rotor blades shows that this noise source can account for the fundamental and first harmonics of the blade frequencies. It is suggested that higher frequences may be due to the absorption of atmospheric turbulence.

Fournier, Francette; Roger, Michel

1989-02-01

234

The Acoustic Analogy and the Prediction of the Noise of Rotating Blades  

Microsoft Academic Search

:   The acoustic analogy was introduced into acoustics by Lighthill in 1952 to understand and predict the noise generated by\\u000a the jet of an aircraft turbojet engine. The idea behind the acoustic analogy is simple but powerful. The entire noise generation\\u000a process is mathematically reduced to the study of wave propagation in a quiescent medium with the effect of flow

F. Farassat; Kenneth S. Brentner

1998-01-01

235

Numerical simulation for prediction of aerodynamic noise characteristics on a HAWT of NREL phase VI  

Microsoft Academic Search

The purpose of this study is to numerically predict the characteristics of aerodynamic noise generated from rotating wind\\u000a turbine blades according to wind speeds using commercial CFD code, FLUENT. The near-field flow around a HAWT of NREL Phase\\u000a VI is simulated directly by LES, whereas the far-field aerodynamic noise for frequencies below 500 Hz is modeled using FW-H\\u000a analogy. As

Jang-Oh Mo; Young-Ho Lee

2011-01-01

236

A Predictive Congestion Control Policy for Broadband Integrated Wide Area Networks  

Microsoft Academic Search

In this paper, we present a predictive congestion control policy for transporting data traffic in a high-speed wide-area network, in the presence of real-time traffic, such as voice and video traffic. The policy is based on information exchange between adjacent nodes of the network. The evolution of the buffer content at a node is determined by the real-time traffic arrival

Gopalakrishnan Ramamurthy; Bhaskar Sengupta

1996-01-01

237

Aircraft noise synthesis system  

NASA Astrophysics Data System (ADS)

A second-generation Aircraft Noise Synthesis System has been developed to provide test stimuli for studies of community annoyance to aircraft flyover noise. The computer-based system generates realistic, time-varying, audio simulations of aircraft flyover noise at a specified observer location on the ground. The synthesis takes into account the time-varying aircraft position relative to the observer; specified reference spectra consisting of broadband, narrowband, and pure-tone components; directivity patterns; Doppler shift; atmospheric effects; and ground effects. These parameters can be specified and controlled in such a way as to generate stimuli in which certain noise characteristics, such as duration or tonal content, are independently varied, while the remaining characteristics, such as broadband content, are held constant. The system can also generate simulations of the predicted noise characteristics of future aircraft. A description of the synthesis system and a discussion of the algorithms and methods used to generate the simulations are provided. An appendix describing the input data and providing user instructions is also included.

McCurdy, David A.; Grandle, Robert E.

1987-02-01

238

JT150 1/2-scale nozzle jet noise experiment and comparison with prediction  

NASA Astrophysics Data System (ADS)

As part of a program to study flight effects on the exhaust noise of a full scale JT15D engine, static half scale model jet noise experiments were conducted. Acoustic data were recorded for microphone angles of 45 deg to 155 deg with jet conditions for the model scale nozzle corresponding closely to those at 55, 73 and 97 percent of corrected rated speed for the full scale engine. These data are useful for determining the relative importance of jet and core noise in the static full scale engine test data and will in turn allow for a proper evaluation of flight effects on the exhaust noise results. The model scale data are also compared with the coaxial jet noise prediction. Above 1000 Hz, the prediction is nominally 0 to 3 dB higher than the data. The arithmetic mean of the differences between the experimental OASPL and the predicted OASPL for all angles for each run ranged from 0 to -3.2 dB. The standard deviation of all the OASPL differences is 2.2 dB. The discrepancies are greatest at low primary jet velocities and appear to be due to inadequacy in the variable jet density exponent incorporated in the prediction procedure.

Groesbeck, D. E.; Wasserbauer, C. A.

1983-05-01

239

Broadband Infrastructure and Economic Growth  

Microsoft Academic Search

We estimate the effect of broadband infrastructure, which enables high-speed internet, on economic growth in the panel of OECD countries in 1996-2007. Our instrumental-variable model derives its non-linear first stage from a logistic diffusion model where pre-existing voice-telephony and cable-TV networks predict maximum broadband penetration. We find that a 10 percentage-point increase in broadband penetration raises annual per-capita growth by

Nina Czernich; Oliver Falck; Tobias Kretschmer; Ludger Woessmann

2009-01-01

240

Broadband Infrastructure and Economic Growth  

Microsoft Academic Search

We estimate the effect of broadband infrastructure, which enables high-speed internet, on economic growth in the panel of OECD countries in 19962007. Our instrumental variable model derives its non-linear first stage from a logistic diffusion model where pre-existing voice telephony and cable TV networks predict maximum broadband penetration. We find that a 10 percentage point increase in broadband penetration raised

Nina Czernich; Oliver Falck; Tobias Kretschmer; Ludger Woessmann

2011-01-01

241

Noise prediction for jetstar prop-fan test  

Microsoft Academic Search

The acoustic calculations reported in this memorandum are for two model prop-fan designs (SR-2 and SR-3 blades) scheduled for test on top of Jetstar aircraft. The predicted acoustic pressure signatures and spectra for selected microphone positions on the fuselage and operating conditions are presented. A detailed presentation of the input data, the acoustic results, and the corrections for microphone fuselage

F. Farassat; R. M. Martin; G. C. Greene

1980-01-01

242

Embracing noise to improve cross-batch prediction accuracy  

PubMed Central

One important application of microarray in clinical settings is for constructing a diagnosis or prognosis model. Batch effects are a well-known obstacle in this type of applications. Recently, a prominent study was published on how batch effects removal techniques could potentially improve microarray prediction performance. However, the results were not very encouraging, as prediction performance did not always improve. In fact, in up to 20% of the cases, prediction accuracy was reduced. Furthermore, it was stated in the paper that the techniques studied require sufficiently large sample sizes in both batches (train and test) to be effective, which is not a realistic situation especially in clinical settings. In this paper, we propose a different approach, which is able to overcome limitations faced by conventional methods. Our approach uses ranking value of microarray data and a bagging ensemble classifier with sequential hypothesis testing to dynamically determine the number of classifiers required in the ensemble. Using similar datasets to those in the original study, we showed that in only one case (<2%) is our performance reduced (by more than -0.05 AUC) and, in >60% of cases, it is improved (by more than 0.05 AUC). In addition, our approach works even on much smaller training data sets and is independent of the sample size of the test data, making it feasible to be applied on clinical studies.

2012-01-01

243

An outdoor noise propagation study to predict the effect of a power plant expansion  

NASA Astrophysics Data System (ADS)

The results of an outdoor noise propagation model using CadnaA were compared to test data obtained on-site. The subject property is the central utility plant of a hospital located in Milwaukee, scheduled to be expanded with the addition of cooling towers. The modeled area was 400 m squared with a resolution grid of 2 m squared. The model was used to validate the observed test data as well as to predict the anticipated noise levels at completion of the expansion. A total of 11 points were investigated and the predicted data were found to match the test values within 2 dB at many locations. The data from the model show that the anticipated noise levels at the East property line will exceed those mandated by local ordinances by 3 dB. The model also predicts that the addition of a three meter absorbing barrier and the use of reduced noise fans for the six cell cooling system will bring the overall noise level from the system into compliance.

Brasovan, Philip J.; Carney, Melinda J.; Cheenne, Dominique J.

2005-04-01

244

Noise prediction for jetstar prop-fan test  

NASA Astrophysics Data System (ADS)

The acoustic calculations reported in this memorandum are for two model prop-fan designs (SR-2 and SR-3 blades) scheduled for test on top of Jetstar aircraft. The predicted acoustic pressure signatures and spectra for selected microphone positions on the fuselage and operating conditions are presented. A detailed presentation of the input data, the acoustic results, and the corrections for microphone fuselage reflection are included. The general trend observed in these calculations is that the acoustically optimized model (using SR-3 blades) is substantially quieter than the model with SR-2 blades. This latter design has conventional straight blades.

Farassat, F.; Martin, R. M.; Greene, G. C.

1980-12-01

245

An evaluation of a computer code based on linear acoustic theory for predicting helicopter main rotor noise  

NASA Astrophysics Data System (ADS)

The considered computer code called the Farassat/Nystrom analysis, is based on a solution of the Ffowcs-Williams-Hawkings equation reported by Farassat (1975). As a result of the discussed evaluation, it is concluded that the Farassat/Nystrom analysis represents a first step on the road to developing a truly comprehensive rotor noise prediction capability. The current code can be useful for investigating helicopter main rotor noise trends at the lower harmonics. With further refinements and the addition of more noise mechanisms, and other noise generating components, such as the tail rotor, its capabilities to predict component and system noise could be greatly expanded.

Davis, S. J.; Egolf, T. A.

246

Blade-vortex interaction noise - Prediction and comparison with flight and wind tunnel tests  

NASA Astrophysics Data System (ADS)

The BVI noise prediction method developed at ONERA is a combination of three computer programs. The first program (MESIR) calculates the geometry and the intensity of the main rotor wake using a free wake analysis. The second program (ARHIS) provides the blade pressure fluctuations induced by the rotor wake even for close interactions. The third code (PARIS), based on the Ffowcs Williams and Hawkings equation, computes the resulting radiated noise. The last two programs have been specially developed to save computing time. The main lines of the computer programs are presented. Emphasis is laid on aerodynamic and acoustic predictions using these three codes. Comparisons are made with two tests: a wind tunnel test of the US Army AH1G-OLS rotor model, and an Aerospatiale Gazelle flight test. Lift coefficients, blade pressures coefficients and radiated noise are compared.

Spiegel, P.; Rahier, G.; Michea, B.

247

Comparison of measured and predicted flight effects on high-bypass coaxial jet exhaust noise  

NASA Astrophysics Data System (ADS)

A recently developed semi-empirical model for predicting the noise generated by conventional-velocity-profile coaxial jets is compared with full-scale flight data and model-scale simulated flight data for high-bypass nozzles. The prediction model has been shown to agree with small-scale static data for primary jet velocities from 215 to 795 m/s for a wide range of area, temperature and velocity ratios between streams. However, there were insufficient model nozzle, simulated flight data available at that time to permit validation of the flight effects prediction. The comparisons presented in this paper demonstrate that the prediction method is also valid in flight.

Stone, J. R.

1983-04-01

248

Predicted signal-noise ratio of a distributed amplifier and lossy PIN photodiode combination  

NASA Astrophysics Data System (ADS)

The distributed amplifier gives a novel approach to a high speed photo-detecting amplifier combination. A 8.34 dB improvement in signal-to-noise ratio for a distributed amplifier is predicted at a bandwidth of 40 GHz over a conventional grounded-source amplifier combination.

Liang, Jia-Yi; Aitchison, Colin S.

1994-08-01

249

Modeling and Prediction of Structure-Borne Seek Noise of Hard Disk Drives  

Microsoft Academic Search

A numerical approach is presented for modeling and predicting the structure-borne seek noise in hard disk drives (HDDs) in time-domain. Rayleigh integral is adopted to relate the transient acceleration of top cover to its radiated sound pressure. A finite element modeling and simulation technique is employed to arrive at the transient vibration response, which is further used as the input

H. Zheng; J. Q. Mou; W. Z. Lin; E. H. Ong

2009-01-01

250

Prediction of airplane aft-cabin noise using statistical energy analysis  

Microsoft Academic Search

Statistical energy analysis (SEA) predictions of turbulent boundary layer and engine exhaust noise in the aft cabin of an airplane have been made and compared to flight data. Measurements of engine shock-cell sound pressure levels, characterized by relatively long correlation lengths and circumferential and axial variation along the fuselage surface, were extrapolated and used as source inputs to an SEA

Andrew K. Fung; Evan B. Davis

2005-01-01

251

Liner Optimization Studies Using the Ducted Fan Noise Prediction Code TBIEM3D.  

National Technical Information Service (NTIS)

In this paper we demonstrate the usefulness of the ducted fan noise prediction code TBIEM3D as a liner optimization design tool. Boundary conditions on the interior duct wall allow for hard walls or a locally reacting liner with axially segmented, circumf...

M. H. Dunn F. Farassat

2004-01-01

252

THE APPLICATION OF A BOUNDARY INTEGRAL EQUATION METHOD TO THE PREDICTION OF DUCTED FAN ENGINE NOISE  

Microsoft Academic Search

The prediction of ducted fan engine noise using a boundary integral equation method (BIEM) is considered. Governing equations for the BIEM are based on linearized acoustics and describe the scattering of incident sound by a thin, finite-length cylindrical duct in the presence of a uniform axial inflow. A classical boundary value problem (BVP) is derived that includes an axisymmetric, locally

M. H. Dunn; J. Tweed; F. Farassat

1999-01-01

253

The influence of real-world rail head roughness on railway noise prediction  

NASA Astrophysics Data System (ADS)

Harmonised methods for the prediction of noise from roads, railways, aviation and industry will eventually be available as a result of the HARMONOISE and IMAGINE EC projects, but not in the immediate future. As the first round of noise mapping under Directive 2002/49/EC is required to be completed in 2007, alternative models are required. The options for railways under the Directive are either to use the Dutch national procedure as the approved EC “interim method” or for Member States to use their own method if it can be adapted to produce results in terms of the indicators required by the Directive. In the UK it is therefore likely that the national method “Calculation of Railway Noise 1995” (CRN) will be applied. This paper discusses a shortcoming in CRN that results from its assumption that the rail head is comparatively smooth. In reality this is often not the case, leading to increased rolling noise levels. A statistically based study has been carried out for the UK Department for Environment, Food and Rural Affairs into the effects of rail head roughness on rolling noise prediction. Correction factors have been devised to account for the true roughness of rails in the UK, either at a local level or across the entire network. The acoustic effectiveness of rail grinding strategies has also been examined.

Hardy, A. E. J.; Jones, R. R. K.; Turner, S.

2006-06-01

254

Noise sampling issues for impact/impulse noise surveys  

NASA Astrophysics Data System (ADS)

Noise-induced hearing loss (NIHL) has been recognized as a serious health concern for decades. ISO Standard 1999:1990 provides a means to predict noise-induced hearing loss (NIHL) based on LAeq measurements in the working environments of workers. This standard seems to work well for predicting hearing loss in continuous noise fields. However, it is possible that ISO 1999 does not apply well to impact, impulsive, or other transient noise fields. NIOSH and University of Pittsburgh are currently developing noise-sampling strategies to measure impact and impulse noise in a manufacturing environment with the aim of developing new impulsive noise metrics. As part of the study, broadband impact/impulse pressure measurements will be made. Issues such as instrumentation, data quality, repeatability, spatial sampling, equipment portability, and calibration are addressed. Also, the annotation, digitization, and editing of the waveforms will be discussed. As part of the project, an archival database of manufacturing impulse/impact will be created to support the future algorithmic development. The ultimate goal of the project is to develop new metrics to characterize the hazards of impact/impulse noise that will complement ISO 1999 for predicting NIHL.

Prince, Mary M.; Vipperman, Jeffrey S.

2003-04-01

255

The state of the art of predicting noise-induced sleep disturbance in field settings.  

PubMed

Several relationships between intruding noises (largely aircraft) and sleep disturbance have been inferred from the findings of a handful of field studies. Comparisons of sleep disturbance rates predicted by the various relationships are complicated by inconsistent data collection methods and definitions of predictor variables and predicted quantities. None of the relationships is grounded in theory-based understanding, and some depend on questionable statistical assumptions and analysis procedures. The credibility, generalizability, and utility of sleep disturbance predictions are also limited by small and nonrepresentative samples of test participants, and by restricted (airport-specific and relatively short duration) circumstances of exposure. Although expedient relationships may be the best available, their predictions are of only limited utility for policy analysis and regulatory purposes, because they account for very little variance in the association between environmental noise and sleep disturbance, have characteristically shallow slopes, have not been well validated in field settings, are highly context-dependent, and do not squarely address the roles and relative importance of nonacoustic factors in sleep disturbance. Such relationships offer the appearance more than the substance of precision and objectivity. Truly useful, population-level prediction and genuine understanding of noise-induced sleep disturbance will remain beyond reach for the foreseeable future, until the findings of field studies of broader scope and more sophisticated design become available. PMID:20472953

Fidell, Sanford; Tabachnick, Barbara; Pearsons, Karl S

256

Prediction of airplane aft-cabin noise using statistical energy analysis  

NASA Astrophysics Data System (ADS)

Statistical energy analysis (SEA) predictions of turbulent boundary layer and engine exhaust noise in the aft cabin of an airplane have been made and compared to flight data. Measurements of engine shock-cell sound pressure levels, characterized by relatively long correlation lengths and circumferential and axial variation along the fuselage surface, were extrapolated and used as source inputs to an SEA model of a widebody airplane fuselage. Turbulent boundary layer pressure fluctuations, characterized by relatively short circumferential correlation lengths and uniformity over the aft fuselage, were represented using Efimtsov empirical correlation functions. Model variance was predicted using the Langley method and combined with estimates of measurement uncertainty to verify the prediction process.

Fung, Andrew K.; Davis, Evan B.

2005-09-01

257

A computational model to predict changes in breathiness resulting from variations in aspiration noise level  

PubMed Central

Perception of breathy voice quality is cued by a number of acoustic changes including an increase in aspiration noise level (AH) and spectral slope[1]. Changes in AH in a vowel may be evaluated through measures such as the harmonic-to-noise ratio (HNR), cepstral peak prominence (CPP) or via auditory measures such as the partial loudness of harmonic energy (PL) and loudness of aspiration noise (NL). Although a number of experiments have reported high correlation between such measures and ratings of perceived breathiness, a formal model to predict breathiness of a vowel has not been proposed. This research describes two computational models to predict changes in breathiness resulting from variations in AH. One model uses auditory measures while the other uses CPP as independent variables to predict breathiness. For both cases, a translated and truncated power function is required to predict breathiness. Some parameters in both of these models were observed to be pitch-dependent. The “unified” model based on auditory measures was observed to be more accurate than one based on CPP.

Shrivastav, Rahul; Camacho, Arturo

2009-01-01

258

Prediction of broadband ground-motion time histories: Hybrid low/high-frequency method with correlated random source parameters  

USGS Publications Warehouse

We present a new method for calculating broadband time histories of ground motion based on a hybrid low-frequency/high-frequency approach with correlated source parameters. Using a finite-difference method we calculate low-frequency synthetics (< ???1 Hz) in a 3D velocity structure. We also compute broadband synthetics in a 1D velocity model using a frequency-wavenumber method. The low frequencies from the 3D calculation are combined with the high frequencies from the 1D calculation by using matched filtering at a crossover frequency of 1 Hz. The source description, common to both the 1D and 3D synthetics, is based on correlated random distributions for the slip amplitude, rupture velocity, and rise time on the fault. This source description allows for the specification of source parameters independent of any a priori inversion results. In our broadband modeling we include correlation between slip amplitude, rupture velocity, and rise time, as suggested by dynamic fault modeling. The method of using correlated random source parameters is flexible and can be easily modified to adjust to our changing understanding of earthquake ruptures. A realistic attenuation model is common to both the 3D and 1D calculations that form the low- and high-frequency components of the broadband synthetics. The value of Q is a function of the local shear-wave velocity. To produce more accurate high-frequency amplitudes and durations, the 1D synthetics are corrected with a randomized, frequency-dependent radiation pattern. The 1D synthetics are further corrected for local site and nonlinear soil effects by using a 1D nonlinear propagation code and generic velocity structure appropriate for the site's National Earthquake Hazards Reduction Program (NEHRP) site classification. The entire procedure is validated by comparison with the 1994 Northridge, California, strong ground motion data set. The bias and error found here for response spectral acceleration are similar to the best results that have been published by others for the Northridge rupture.

Liu, P.; Archuleta, R. J.; Hartzell, S. H.

2006-01-01

259

Measurement and prediction of noise from low-altitude military aircraft operations  

NASA Astrophysics Data System (ADS)

In response to the rapid growth in demand for information on noise levels around military airfields in the UK, NPL developed AIRNOISE, a mathematical model for computing aircraft noise contours. Since its first applications in 1981, the model has been used to determine zones of eligibility within the MoD compensation scheme. The model has been subject to continuous development, e.g., the incorporation of Harrier V/STOL operations. We have now extended the model to include noise from high-speed, low-level operations. The model predicts not only maximum levels but the complete time-history, so that the time-onset rate can be estimated. To aid refinement and validation of the model, a special exercise has been conducted in which Tornado, Harrier, Jaguar, Hawk, F-15 and F-16 aircraft have flown straight and level at heights between about 100 and 400 feet, at various speeds and engine power settings over an array of microphones. This paper describes the trial and the results obtained. The prediction model is outlined and comparisons made between predictions and measurements.

Barry, Bernard F.; Payne, Richard C.; Harris, Anthony L.; Weston, Ralph J.

1992-04-01

260

The Application of a Boundary Integral Equation Method to the Prediction of Ducted Fan Engine Noise  

NASA Astrophysics Data System (ADS)

The prediction of ducted fan engine noise using a boundary integral equation method (BIEM) is considered. Governing equations for the BIEM are based on linearized acoustics and describe the scattering of incident sound by a thin, finite-length cylindrical duct in the presence of a uniform axial inflow. A classical boundary value problem (BVP) is derived that includes an axisymmetric, locally reacting liner on the duct interior. Using potential theory, the BVP is recast as a system of hypersingular boundary integral equations with subsidiary conditions. We describe the integral equation derivation and solution procedure in detail. The development of the computationally efficient ducted fan noise prediction program TBIEM3D, which implements the BIEM, and its utility in conducting parametric noise reduction studies are discussed. Unlike prediction methods based on spinning mode eigenfunction expansions, the BIEM does not require the decomposition of the interior acoustic field into its radial and axial components which, for the liner case, avoids the solution of a difficult complex eigenvalue problem. Numerical spectral studies are presented to illustrate the nexus between the eigenfunction expansion representation and BIEM results. We demonstrate BIEM liner capability by examining radiation patterns for several cases of practical interest.

Dunn, M. H.; Tweed, J.; Farassat, F.

1999-11-01

261

Predicting stochastic systems by noise sampling, and application to the El Niño-Southern Oscillation.  

PubMed

Interannual and interdecadal prediction are major challenges of climate dynamics. In this article we develop a prediction method for climate processes that exhibit low-frequency variability (LFV). The method constructs a nonlinear stochastic model from past observations and estimates a path of the "weather" noise that drives this model over previous finite-time windows. The method has two steps: (i) select noise samples--or "snippets"--from the past noise, which have forced the system during short-time intervals that resemble the LFV phase just preceding the currently observed state; and (ii) use these snippets to drive the system from the current state into the future. The method is placed in the framework of pathwise linear-response theory and is then applied to an El Niño-Southern Oscillation (ENSO) model derived by the empirical model reduction (EMR) methodology; this nonlinear model has 40 coupled, slow, and fast variables. The domain of validity of this forecasting procedure depends on the nature of the system's pathwise response; it is shown numerically that the ENSO model's response is linear on interannual time scales. As a result, the method's skill at a 6- to 16-month lead is highly competitive when compared with currently used dynamic and statistic prediction methods for the Niño-3 index and the global sea surface temperature field. PMID:21730171

Chekroun, Mickaël David; Kondrashov, Dmitri; Ghil, Michael

2011-07-05

262

A semi-analytical model for the prediction of underwater noise from offshore pile driving  

NASA Astrophysics Data System (ADS)

Underwater noise from offshore pile driving gained considerable attention in recent years mainly due to the large scale construction of offshore wind farms. The most common foundation type of a wind turbine is a monopile, upon which the wind tower rests. The pile is driven into place with the help of hydraulic hammers. During the hammering of the pile, high levels of noise are generated which are known to produce deleterious effects on both mammals and fish. In this work, a linear semi-analytical model is developed for predicting the levels of underwater noise for a wide range of system parameters. The model incorporates all major parts of the system. The hydraulic hammer is substituted by an external force, the pile is described as a thin circular cylindrical shell, the water is modelled as a compressible fluid and the water-saturated seabed is defined by distributed springs and dashpots in all directions. The solution of the coupled vibroacoustic problem is based on the representation of the response of the complete system on the modal basis of the in vacuo shell structure. The influence that the inter-modal coupling, the choice of the soil parameters and the acoustic impedance of the seabed have on the generated noise levels is studied in the frequency domain. Strong and weak points of the present model are discussed on the basis of a comparison with a set of available experimental data. The obtained results show the capability of the model to predict the underwater noise levels both qualitatively and quantitatively.

Tsouvalas, A.; Metrikine, A. V.

2013-06-01

263

Broadband teleportation  

Microsoft Academic Search

Quantum teleportation of an unknown broadband electromagnetic field is investigated. The continuous-variable teleportation protocol by Braunstein and Kimble [Phys. Rev. Lett. 80, 869 (1998)] for teleporting the quantum state of a single mode of the electromagnetic field is generalized for the case of a multimode field with finite bandwith. We discuss criteria for continuous-variable teleportation with various sets of input

P. van Loock; Samuel L. Braunstein; H. J. Kimble

2000-01-01

264

Prediction of blade-vortex interaction noise using measured blade pressures  

NASA Astrophysics Data System (ADS)

In the study reported here, blade-vortex interaction noise was predicted using a simplified model of blade pressures measured on a one-seventh scale model AH-1/OLS main rotor. The methods used for the acoustic prediction are based on the acoustic analogy and have been developed by Nakamura (1981) and by Brentner, Nystrom, and Farassat (referred to as the WOPWOP method). The waveforms predicted by the two methods are in good agreement with each other and with the measurements in terms of the number of pulses, the pulse widths, and the separation times between the pulses. The peak amplitude of the dominant pulse may, however, be underpredicted by up to 40 percent, depending on flight conditions. Ways of improving the accuracy of the prediction methods are suggested.

Joshi, Mahendra C.; Liu, Sandy R.; Boxwell, Donald A.

1987-10-01

265

Experimental study of tyre/road contact forces in rolling conditions for noise prediction  

NASA Astrophysics Data System (ADS)

This paper deals with the experimental study of dynamical tyre/road contact for noise prediction. In situ measurements of contact forces and close proximity noise levels were carried out for a slick tyre rolling on six different road surfaces between 30 and 50 km/h. Additional texture profiles of the tested surfaces were taken on the wheel track. Normal contact stresses were measured at a sampling frequency of 10752 Hz using a line of pressure sensitive cells placed both along and perpendicular to the rolling direction. The contact areas obtained during rolling were smaller than in static conditions. This is mainly explained by the dynamical properties of tyre compounds, like the viscoelastic behaviour of the rubber. Additionally the root-mean-square of the resultant contact forces at various speeds was in the same order for a given road surface, while their spectra were quite different. This is certainly due to a spectral influence of bending waves propagating in the tyre during rolling, especially when the wavelength is small in comparison with the size of the contact patch. Finally, the levels of contact forces and close proximity noise measured at 30 km/h were correlated. Additional correlations with texture levels were performed. The results show that the macro-texture generates contact forces linearly around 800 Hz and consequently noise levels between 500 and 1000 Hz via the vibrations transmitted to the tyre.

Cesbron, Julien; Anfosso-Lédée, Fabienne; Duhamel, Denis; Ping Yin, Hai; Le Houédec, Donatien

2009-02-01

266

On the prediction of impact noise, III: Energy accountancy in industrial machines  

NASA Astrophysics Data System (ADS)

It has been explained in the two previous parts of this series of papers that the peak noise level of an impact machine can be predicted in terms of the initial kinetic energy in an equivalent bag of air of the same dimensions and impact time, but that the total Leq at any frequency must depend upon the vibrational energy stored in the machine following impact and in its ability to radiate such energy as sound. This paper presents a method of examining the energy balance in the machine and obtains simple and helpful expressions for the radiated sound energy in terms of the internal energy level, a ``modified'' radiation efficiency, a structural damping factor, and a bulkness factor (equation (4a)). An alternative form, based upon the measured rates of change of force in the operating tool, impulse and structural response factors, modified radiation efficiency, damping factor and bulkiness factor is also presented (equation (4b)). The diagnostic advantages of thinking in terms of the changes in each of these terms as a method of studying noise control, even for apparently continuous running processes, are illustrated by a series of case studies which include punch press analysis, bottle impacts, impacts of solid workpieces falling into bins, gearwheel noise phenomena, backlash and diesel engine noise.

Richards, E. J.

1981-05-01

267

SR-3 prop fan noise prediction based on time domain method  

NASA Astrophysics Data System (ADS)

This paper presents a numerical technique for the prediction of the noise of SR-3 prop-fan. The blades upper and lower surfaces are described by a helical coordinate system which also used to divide blade surfaces into panels. Two different acoustic formulation in the time domain are used to improve the speed and the efficiency of the noise calculation: Woan and Gregorek's formulation for panels moving at subsonic speeds and Farassat's collapsing sphere formulation for panels moving at transonic or supersonic speeds. The surface pressure data are obtained by a 3D Euler code which uses Ni's one step distribution formula and multigrid technique. A grid size study for accuracy and speed of execution on a computer is also presented.

Kim, Yong S.; Rho, Oh H.

268

Noise performance of IRIS/IDA broadband seismic stations AAK and TLY in the USSR. Quarterly technical report No. 1, 1 Feb-30 Sep 91  

SciTech Connect

Absolute ground noise levels (power spectral amplitude vs. frequency) were calculated from .001 Hz to 10 Hz for two seismic stations in the USSR deployed by Project IDA in fall of 1990. The stations are located at Ala-Archa, Kirghizia (AAK; lat-42.639 degree N, Ion 74.494 degree E, elev 1645 m) and Talaya, in Siberia (TLY; lat 51.681 degree N,Ion 103.644 degree E, elev 579 m). Findings can be summarized as follows: Station AAK shows the lowest average absolute nighttime noise levels above 1 Hz documented to date for IDA USSR stations. Ground noise increases during the day over night levels at AAK, with the maximum increase (7-9 dB) occuring between 2-3 Hz. Below .7 Hz, day and night noise levels are the same at AAK. TLY average nighttime ground noise levels are about 6-10 dB higher than AAK levels above 1 Hz. Below .6 Hz, nighttime levels at AAK and TLY are comparable, except that TLY has lower horizontal noise levels (4-5 dB) at periods longer than 25 s. Almost no difference between night and day noise levels was observed at TLY; in this sense it is unique among the IDA USSR stations.

Given, H.K.

1991-11-18

269

Development of a prediction method for flow-generated noise produced by duct elements in ventilation systems  

Microsoft Academic Search

Flow-generated noise generated on the quiet side of the primary attenuators of a ventilation system is the result of interaction between air flow and duct discontinuities. It is of engineering importance to predict the flow-generated noise caused by air duct elements in ventilation systems at the design stage. However, all prediction methods are based upon an isolated in-duct element that

C. M. Mak

2002-01-01

270

Development of computer program ENMASK for prediction of residual environmental masking-noise spectra, from any three independent environmental parameters  

SciTech Connect

Residual environmental sound can mask intrusive4 (unwanted) sound. It is a factor that can affect noise impacts and must be considered both in noise-impact studies and in noise-mitigation designs. Models for quantitative prediction of sensation level (audibility) and psychological effects of intrusive noise require an input with 1/3 octave-band spectral resolution of environmental masking noise. However, the majority of published residual environmental masking-noise data are given with either octave-band frequency resolution or only single A-weighted decibel values. A model has been developed that enables estimation of 1/3 octave-band residual environmental masking-noise spectra and relates certain environmental parameters to A-weighted sound level. This model provides a correlation among three environmental conditions: measured residual A-weighted sound-pressure level, proximity to a major roadway, and population density. Cited field-study data were used to compute the most probable 1/3 octave-band sound-pressure spectrum corresponding to any selected one of these three inputs. In turn, such spectra can be used as an input to models for prediction of noise impacts. This paper discusses specific algorithms included in the newly developed computer program ENMASK. In addition, the relative audibility of the environmental masking-noise spectra at different A-weighted sound levels is discussed, which is determined by using the methodology of program ENAUDIBL.

Chang, Y.-S.; Liebich, R. E.; Chun, K. C.

2000-03-31

271

Flow instability in turbomachinery and the prediction of the emitted noise spectrum  

NASA Astrophysics Data System (ADS)

A method is presented for predicting the distribution of energy between spectral peaks and wideband structure in the noise spectrum produced by flow instability relative to turbomachine rotor blades. Interactions between unsteady flow perturbations and successive blades are represented as pulse trains, to which modulations in phase and amplitude are possible. The special cases of modulation in amplitude only and amplitude modulation without mutual correlations and appearance time modulation are examined, and predictions are compared with the experimental measurements of Michel (1980) of the pressure distribution in an axial fan rotor in the wake of a rod. The method is shown to be capable of predicting both the sound level and the spectral broadening of harmonics of the frequency of blade passage of order three or greater.

Sunyach, M.

1980-11-01

272

Broadband teleportation  

Microsoft Academic Search

Quantum teleportation of an unknown broadband electromagnetic field is\\u000ainvestigated. The continuous-variable teleportation protocol by Braunstein and\\u000aKimble [Phys. Rev. Lett. {\\\\bf 80}, 869 (1998)] for teleporting the quantum\\u000astate of a single mode of the electromagnetic field is generalized for the case\\u000aof a multimode field with finite bandwith. We discuss criteria for\\u000acontinuous-variable teleportation with various sets of

P. van Loock; Samuel L. Braunstein; H. J. Kimble

2000-01-01

273

Low-level otoacoustic emissions may predict susceptibility to noise-induced hearing loss.  

PubMed

In a longitudinal study with 338 volunteers, audiometric thresholds and otoacoustic emissions were measured before and after 6 months of noise exposure on an aircraft carrier. While the average amplitudes of the otoacoustic emissions decreased significantly, the average audiometric thresholds did not change. Furthermore, there were no significant correlations between changes in audiometric thresholds and changes in otoacoustic emissions. Changes in transient-evoked otoacoustic emissions and distortion-product otoacoustic emissions were moderately correlated. Eighteen ears acquired permanent audiometric threshold shifts. Only one-third of those ears showed significant otoacoustic emission shifts that mirrored their permanent threshold shifts. A Bayesian analysis indicated that permanent threshold shift status following a deployment was predicted by baseline low-level or absent otoacoustic emissions. The best predictor was transient-evoked otoacoustic emission amplitude in the 4-kHz half-octave frequency band, with risk increasing more than sixfold from approximately 3% to 20% as the emission amplitude decreased. It is possible that the otoacoustic emissions indicated noise-induced changes in the inner ear, undetected by audiometric tests. Otoacoustic emissions may therefore be a diagnostic predictor for noise-induced-hearing-loss risk. PMID:16875225

Lapsley Miller, Judi A; Marshall, Lynne; Heller, Laurie M; Hughes, Linda M

2006-07-01

274

Ambient seismic noise monitoring of a clay landslide: Toward failure prediction  

NASA Astrophysics Data System (ADS)

Given that clay-rich landslides may become mobilized, leading to rapid mass movements (earthflows and debris flows), they pose critical problems in risk management worldwide. The most widely proposed mechanism leading to such flow-like movements is the increase in water pore pressure in the sliding mass, generating partial or complete liquefaction. This solid-to-liquid transition results in a dramatic reduction of mechanical rigidity in the liquefied zones, which could be detected by monitoring shear wave velocity variations. With this purpose in mind, the ambient seismic noise correlation technique has been applied to measure the variation in the seismic surface wave velocity in the Pont Bourquin landslide (Swiss Alps). This small but active composite earthslide-earthflow was equipped with continuously recording seismic sensors during spring and summer 2010. An earthslide of a few thousand cubic meters was triggered in mid-August 2010, after a rainy period. This article shows that the seismic velocity of the sliding material, measured from daily noise correlograms, decreased continuously and rapidly for several days prior to the catastrophic event. From a spectral analysis of the velocity decrease, it was possible to determine the location of the change at the base of the sliding layer. These results demonstrate that ambient seismic noise can be used to detect rigidity variations before failure and could potentially be used to predict landslides.

Mainsant, Guénolé; Larose, Eric; Brönnimann, Cornelia; Jongmans, Denis; Michoud, Clément; Jaboyedoff, Michel

2012-03-01

275

Methods and Tools for Monitoring and Prediction of the Large-Scale Environmental Impact of Railway Noise  

NASA Astrophysics Data System (ADS)

Due to environmental impact regulations there is a demand for methods and tools to determine noise reception levels near railway lines. Currently, a wide variety of methods and tools is available. Fast computers now enable us to develop powerful tools that combine simplified prediction methods with GIS systems. These new systems allow the study of noise reception levels and environmental impact on a large-scale (complete network, national or international), while more detailed and labour-intensive methods and tools are used when demanded by law. This paper presents a brief overview of the noise prediction methods and tools used in the Netherlands. The focus is on the advantages and restrictions of the different methods. Finally, the paper gives an overview of the actual advantages and restrictions of the recently extended Gerano method Gerano98 (Geographic Railway Noise). Gerano was originally based on the ``basic Dutch calculation rules for railway noise''. Gerano98 was extended using simplified prediction schemes for the most relevant parts of the ``detailed Dutch calculation rules for railway noise''. This most recent calculation method, combined with geographic input features, provides the possibility of determining noise impact and the noise measures to be taken on both the medium and large scale. Examples of the application of the methods and tools to specific (medium- and large-scale) projects are provided. The medium-scale project presents the results of a selection of the prefered line between Amsterdam and Zwolle. The large-scale project (the complete Dutch railway network) shows the results of the comparison of noise measures at source with noise barriers or housing insulation. For both projects the applicability and the usefulness of the methods in these situations is discussed. In conclusion four developments of the Gerano concept are described which have recently been finished or will be so in the near future.

Elbers, F. B. J.

2000-03-01

276

Real-Scale Measurement Results for Audible Noise from AC Overhead Transmission Lines and Prediction Formula in Heavy Rain  

NASA Astrophysics Data System (ADS)

The audible noise produced by corona discharge from AC overhead transmission line conductors is one of the major factors affecting the design of conductors, particularly for transmission lines with voltages above 500 kV. The audible noise has two components, which are random noise with frequency components from several hundreds to 20 kHz and pure tones with a power line frequency and frequency components of its even multiples. In this paper, measurement results for random noise in heavy rain using a real-scale facility, namely, UHV corona cage, which has a cross section of 8 m×8 m and a length of 24 m, are shown and a new prediction formula for the sound level of random noise in heavy rain is proposed.

Tanabe, Kazuo

277

Interior Noise Reduction of Enclosure Using Predicted Characteristics of Porous Material  

NASA Astrophysics Data System (ADS)

In this paper, the objective is to reduce the interior noise in a specific frequency band by using the predicted acoustical characteristics of a porous material. To identify the interior sound field of an enclosure, the Green’s function is used and the analytical results are verified by comparing with experimental results. Foamed aluminum is used an absorption material to used as absorption materials to reduce the interior sound pressure of the enclosure. Foamed aluminum is generally known as a metallic porous sound absorption material that has desirable attributes such as lightweight and high absorbing performance. Predicted acoustical parameters of foamed aluminum are used in the analysis to predict sound pressure levels in an enclosure and these results are compared with those of the experiments. To verify the predicted characteristics of the porous material, the analytical results obtained for the acoustical transmission matrix are compared with the experimentally obtained results from a two-microphone arrangement. Based on these results, an appropriate thickness of foamed aluminum is provided for pressure reduction in a specific frequency band.

Oh, Jae-Eung; Kim, Wootaek

278

Sound-quality prediction for nonstationary vehicle interior noise based on wavelet pre-processing neural network model  

Microsoft Academic Search

A new concept for sound-quality prediction, the so-called wavelet pre-processing neural network (WT-NN) model, is presented in this paper. Based on interior vehicle noise, the WT-NN sound-quality evaluation model was developed by combining the techniques of wavelet analysis and neural network (NN) classification. A wavelet-based 21-point model for vehicle noise feature extraction was established, as was a NN model. Verification

Y. S. Wang; C.-M. Lee; D.-G. Kim; Y. Xu

2007-01-01

279

A NUMERICAL STUDY OF FLUID FLOW PAST A CIRCULAR CYLINDER AT RE=3900 AND A PRACTICAL APPROACH TO NOISE PREDICTION  

Microsoft Academic Search

The aim of this study is the prediction of the aerodynamic noise generated by the fluid flow past a circular cylinder at Re=3900, combining numerical simulation of the fluid flow with an analytical noise evaluation. This case has been extended to the flow around a cylinder with Re=140000. The Large Eddy Simulation (LES) turbulence model of FLUENT v6.3 is used

A. Pradera; G. Keith; F. Jacobsen; N. Gil-Negrete; A. Rivas

280

A reduced-scale railway noise barrier's insertion loss and absorption coefficients: comparison of field measurements and predictions  

NASA Astrophysics Data System (ADS)

In situ testing determined the insertion loss (IL) and absorption coefficients of a candidate absorptive noise barrier (soundwall) to abate railway noise for residents of Anaheim, CA. A 4000m barrier is proposed south of the tracks, but residential areas to the north have expressed concerns that barrier reflections will increase their noise exposure. To address these concerns, a 3.66m high by 14.6m long demonstration barrier was built in the parking lot of Edison Field, Anaheim, as part of a public open house, thereby allowing for acoustical measurements. Insertion loss (IL) was measured in third-octave bands assuming 1/2-scale construction. The IL for three, scaled railway noise sub-sources (rail/wheel interface, locomotive, and train horn) was measured at six, scaled distances. The highest total, A-weighted IL, after corrections for finite-barrier and point-source speaker effects was 22dB(A) for rail/wheel noise, 18dB(A) for locomotive noise, and 20dB(A) for train horn noise. These results can be compared favourably to IL predictions made using algorithms from the US Federal Rail Administration (FRA) noise assessment guidelines. For the actual barrier installation, shielded residential receivers located south of the project are expected to see their future noise exposures reduced from an unmitigated 78 CNEL to 65 CNEL. Absorption coefficients were measured using time delay spectrometry. At lower frequencies, measured absorption coefficients were notably less than the reverberation room results advertised in the manufacturer's literature, but generally conformed with impedance tube results. At higher frequencies the correspondence between measured absorption coefficients and reverberation room results was much improved. For the actual barrier installation, unshielded residential receivers to the north are expected to experience noise exposure increases of less than 1dB(A). This factor of increase is consistent with a finding of no impact when assessed using FRA guidelines for allowable increases of noise exposure.

Busch, T. A.; Nugent, R. E.

2003-10-01

281

Theoretical predictions and actual hearing threshold levels in workers exposed to ultrasonic noise of impulsive character--a pilot study.  

PubMed

Results of standard pure-tone audiometry (PTA) were collected from 25 workers, mainly females, aged 23-58 years, exposed for 2-13 years to ultrasonic noise emitted by ultrasonic welders. Hearing tests were completed by evaluation of exposure to ultrasonic noise. The subjects' actual audiometric hearing threshold levels (HTLs) were compared with theoretical predictions calculated according to ISO 1999:1990. In 60% of cases sound pressure levels in the 10-40 kHz 1/3-octave bands at workstands exceeded Polish exposure limits for ultrasonic noise. Our comparison of predicted and measured HTLs suggests that the ISO 1999:1990 method, intended for audible noise, might also make it possible to predict reliably permanent hearing loss (in the 2000-6000 Hz frequency range) after exposure to ultrasonic noise. No significant progress of hearing impairment (assessed using PTA) in the operators of ultrasonic welders was noted. Nevertheless, further studies on the hearing status of workers exposed to ultrasonic noise are needed. PMID:18082023

Pawlaczyk-?uszczy?ska, Ma?gorzata; Dudarewicz, Adam; Sliwi?ska-Kowalska, Mariola

2007-01-01

282

A moving medium formulation for prediction of propeller noise at incidence  

NASA Astrophysics Data System (ADS)

This paper presents a time domain formulation for the sound field radiated by moving bodies in a uniform steady flow with arbitrary orientation. The aim is to provide a formulation for prediction of noise from body so that effects of crossflow on a propeller can be modeled in the time domain. An established theory of noise generation by a moving source is combined with the moving medium Green's function for derivation of the formulation. A formula with Doppler factor is developed because it is more easily interpreted and is more helpful in examining the physic of systems. Based on the technique presented, the source of asymmetry of the sound field can be explained in terms of physics of a moving source. It is shown that the derived formulation can be interpreted as an extension of formulation 1 and 1A of Farassat based on the Ffowcs Williams and Hawkings (FW-H) equation for moving medium problems. Computational results for a stationary monopole and dipole point source in moving medium, a rotating point force in crossflow, a model of helicopter blade at incidence and a propeller case with subsonic tips at incidence verify the formulation.

Ghorbaniasl, Ghader; Lacor, Chris

2012-01-01

283

Large-eddy simulation for the prediction of supersonic rectangular jet noise  

NASA Astrophysics Data System (ADS)

We investigate the noise from isothermal and heated under-expanded supersonic turbulent jets issuing from a rectangular nozzle of aspect ratio 4:1 using high-fidelity unstructured large-eddy simulation (LES) and acoustic projection based on the Ffowcs-Williams Hawkings (FWH) equations. The nozzle/flow interaction is directly included by simulating the flow in and around the nozzle in addition to the jet plume downstream. A grid resolution study is performed and results are shown for unstructured meshes containing up to 300 million control volumes, generated by a massively parallel code scaled to as many as 65,536 processors. Validated against laboratory measurements using a nozzle of precisely the same geometry, we find that mesh isotropy is a key factor in determining the quality of the far-field aeroacoustic predictions. The full flow fields produced by the simulation, in conjunction with particle image velocimetry (PIV) data measured from experiment, allow for a detailed examination of the interaction of large-scale coherent flow features and the resultant far-field noise, and its subsequent modification in the presence of heating.

Nichols, Joseph W.; Ham, Frank E.; Lele, Sanjiva K.; Bridges, James E.

2011-11-01

284

Prediction of aerodynamic noise in a ring fan based on wake characteristics  

NASA Astrophysics Data System (ADS)

A ring fan is a propeller fan that applies an axial-flow impeller with a ring-shaped shroud on the blade tip side. In this study, the entire flow field of the ring fan is simulated using computational fluid dynamics (CFD); the accuracy of the CFD is verified through a comparison with the aerodynamic characteristics of a propeller fan of current model. Moreover, the aerodynamic noise generated by the fan is predicted on the basis of the wake characteristics. The aerodynamic characteristic of the ring fan based on CFD can represent qualitatively the variation in the measured value. The main flow domain of the ring fan is formed at the tip side of the blade because blade tip vortex is not formed at that location. Therefore, the relative velocity of the ring fan is increased by the circumferential velocity. The sound pressure levels of the ring fan within the frequency band of less than 200 Hz are larger than that of the propeller fan. In the analysis of the wake characteristics, it revealed that Karman vortex shedding occurred in the main flow domain in the frequency domain lower than 200 Hz; the aerodynamic noise of the ring fan in the vortex shedding frequency enlarges due to increase in the relative velocity and the velocity fluctuation.

Sasaki, Soichi; Fukuda, Masaharu; Tsujino, Masao; Tsubota, Haruhiro

2011-06-01

285

Color image lossy compression based on blind evaluation and prediction of noise characteristics  

NASA Astrophysics Data System (ADS)

The paper deals with JPEG adaptive lossy compression of color images formed by digital cameras. Adaptation to noise characteristics and blur estimated for each given image is carried out. The dominant factor degrading image quality is determined in a blind manner. Characteristics of this dominant factor are then estimated. Finally, a scaling factor that determines quantization steps for default JPEG table is adaptively set (selected). Within this general framework, two possible strategies are considered. A first one presumes blind estimation for an image after all operations in digital image processing chain just before compressing a given raster image. A second strategy is based on prediction of noise and blur parameters from analysis of RAW image under quite general assumptions concerning characteristics parameters of transformations an image will be subject to at further processing stages. The advantages of both strategies are discussed. The first strategy provides more accurate estimation and larger benefit in image compression ratio (CR) compared to super-high quality (SHQ) mode. However, it is more complicated and requires more resources. The second strategy is simpler but less beneficial. The proposed approaches are tested for quite many real life color images acquired by digital cameras and shown to provide more than two time increase of average CR compared to SHQ mode without introducing visible distortions with respect to SHQ compressed images.

Ponomarenko, Nikolay N.; Lukin, Vladimir V.; Egiazarian, Karen O.; Lepisto, Leena

2011-02-01

286

An evaluation of a computer code based on linear acoustic theory for predicting helicopter main rotor noise  

NASA Astrophysics Data System (ADS)

Acoustic characteristics predicted using a recently developed computer code were correlated with measured acoustic data for two helicopter rotors. The analysis, is based on a solution of the Ffowcs-Williams-Hawkings (FW-H) equation and includes terms accounting for both the thickness and loading components of the rotational noise. Computations are carried out in the time domain and assume free field conditions. Results of the correlation show that the Farrassat/Nystrom analysis, when using predicted airload data as input, yields fair but encouraging correlation for the first 6 harmonics of blade passage. It also suggests that although the analysis represents a valuable first step towards developing a truly comprehensive helicopter rotor noise prediction capability, further work remains to be done identifying and incorporating additional noise mechanisms into the code.

Davis, S. J.; Egolf, T. A.

1980-07-01

287

Identification of the CAGE, Prism, and Book Isomers of Water Hexamer and the Predicted Lowest Energy Heptamer and Nonamer Clusters by Broadband Rotational Spectroscopy  

NASA Astrophysics Data System (ADS)

The water hexamer is predicted to be the smallest water cluster with a three-dimensional hydrogen bonding network as its minimum energy structure. Calculations indicate that there are several possible low-energy isomers, with different levels of theory identifying different isomers as the global minimum. Previous experimental work has provided evidence for the cage, book, and cyclic isomers but no experiment has identified multiple coexisting structures. Using broadband rotational spectroscopy in pulsed supersonic expansion these three isomers have now been unambiguously identified and their oxygen framework structures determined by means of H_218O substitution. Relative isomer populations at different expansion conditions establish that the cage isomer is the minimum energy structure. The comparison of experimental and theoretical rotational constants shows that significant improvement in the agreement is achieved when vibrationally averaged (0 K) theoretical structures are used. For the water hexamer isomers, only the prism shows effects from tunneling associated with the rearrangement of the H-bond network. This tunneling is quenched upon the incorporation of a single H_218O monomer into the prism cluster. Rotational spectra consistent with predictions for the lowest energy heptamer and nonamer structures have also been identified and the structure of the heptamer oxygen atom framework has also been determined using H_218O substitution.

Perez, Cristobal; Muckle, Matt T.; Zaleski, Daniel P.; Seifert, Nathan; Pate, Brooks H.; Kisiel, Zbigniew; Temelso, Berhane; Shields, George C.

2012-06-01

288

Role of community tolerance level (CTL) in predicting the prevalence of the annoyance of road and rail noise.  

PubMed

Fidell et al. [(2011), J. Acoust. Soc. Am. 130(2), 791-806] have shown (1) that the rate of growth of annoyance with noise exposure reported in attitudinal surveys of the annoyance of aircraft noise closely resembles the exponential rate of change of loudness with sound level, and (2) that the proportion of a community highly annoyed and the variability in annoyance prevalence rates in communities are well accounted for by a simple model with a single free parameter: a community tolerance level (abbreviated CTL, and represented symbolically in mathematical expressions as L(ct)), expressed in units of DNL. The current study applies the same modeling approach to predicting the prevalence of annoyance of road traffic and rail noise. The prevalence of noise-induced annoyance of all forms of transportation noise is well accounted for by a simple, loudness-like exponential function with community-specific offsets. The model fits all of the road traffic findings well, but the prevalence of annoyance due to rail noise is more accurately predicted separately for interviewing sites with and without high levels of vibration and/or rattle. PMID:22501056

Schomer, Paul; Mestre, Vincent; Fidell, Sanford; Berry, Bernard; Gjestland, Truls; Vallet, Michel; Reid, Timothy

2012-04-01

289

A boundary-element method using broadband vibrating-wall sources to predict high-frequency interior sound fields produced by wall vibration  

Microsoft Academic Search

In the high-frequency limit, vibrating panels subject to spatially random, temporally broadband forcing are shown to have broadband power and directivity properties than can be characterized by a limited set of parameters, based on numerical simulations. The radiated pressure field is parametrized in terms of direction, wave speed ratio, panel damping, and dimensionless frequency. A source directivity equation dependent on

Linda P. Franzoni; Tracy A. Duvall

2005-01-01

290

A Predictable Robust Fully Programmable Analog Gaussian Noise Source for Mixed-Signal\\/Digital ATE  

Microsoft Academic Search

A robust programmable analog Gaussian noise generator suitable for mixed-signal\\/digital ATEs is presented. Unlike conventional methods (LFSR based noise generators or resistor thermal noise amplification techniques), the user has full control of the characteristics of the Gaussian signal. Indeed, the frequency band, the mean, and variance of the distribution are fully programmable over the voltage range within the supply rails.

Sadok Aouini; Gordon W. Roberts

2006-01-01

291

Microscopic prediction of speech recognition for listeners with normal hearing in noise using an auditory model.  

PubMed

This study compares the phoneme recognition performance in speech-shaped noise of a microscopic model for speech recognition with the performance of normal-hearing listeners. "Microscopic" is defined in terms of this model twofold. First, the speech recognition rate is predicted on a phoneme-by-phoneme basis. Second, microscopic modeling means that the signal waveforms to be recognized are processed by mimicking elementary parts of human's auditory processing. The model is based on an approach by Holube and Kollmeier [J. Acoust. Soc. Am. 100, 1703-1716 (1996)] and consists of a psychoacoustically and physiologically motivated preprocessing and a simple dynamic-time-warp speech recognizer. The model is evaluated while presenting nonsense speech in a closed-set paradigm. Averaged phoneme recognition rates, specific phoneme recognition rates, and phoneme confusions are analyzed. The influence of different perceptual distance measures and of the model's a-priori knowledge is investigated. The results show that human performance can be predicted by this model using an optimal detector, i.e., identical speech waveforms for both training of the recognizer and testing. The best model performance is yielded by distance measures which focus mainly on small perceptual distances and neglect outliers. PMID:19894841

Jürgens, Tim; Brand, Thomas

2009-11-01

292

Mean-squared error and threshold SNR prediction of maximum-likelihood signal parameter estimation with estimated colored noise covariances  

Microsoft Academic Search

An interval error-based method (MIE) of predicting mean squared error (MSE) performance of maximum-likelihood estimators (MLEs) is extended to the case of signal parameter estimation requiring intermediate estimation of an unknown colored noise covariance matrix; an intermediate step central to adaptive array detection and parameter estimation. The successful application of MIE requires good approximations of two quantities: 1) interval error

Christ D. Richmond

2006-01-01

293

MOSFET noise modeling and parameter extraction  

NASA Astrophysics Data System (ADS)

With the recent advances in CMOS technologies, the MOSFETs offer competitive low noise performance at high frequencies comparable with their bipolar counterparts and become attractive candidates even for challenging high frequency applications with their low cost and high integration level. Therefore, the transistor model accuracy becomes a crucial factor for predicting the RF circuit performance accurately in a broad frequency range. An overview of a high frequency noise modeling approach based on a direct parameter extraction technique is presented in this paper. Moreover, the presented parameter extraction methods are evaluated by means of broadband noise parameter and S-parameter measurements. A temperature noise model predicts all four noise parameters at any frequency and can be used to determine the dominant noise source of the small-signal equivalent circuit. The model can be verified by comparing the measured noise parameters with the simulation results over a broad frequency range. Finally, a practical circuit example of an amplifier using a 0.12 ?m CMOS technology at 24 GHz is given.

Berroth, Manfred; Basaran, Umut

2004-05-01

294

Prediction of wake-interaction noise in axial-flow machines - Application to helicopter fenestron  

NASA Astrophysics Data System (ADS)

A wake model based on experimental measurements is used to determine the noise generated by rotor-stator interactions in an axial-flow machine. Application of the model to the tail rotor of a helicopter shows that the 3rd to 9th harmonics of the blade passing frequency can be attributed to this noise source. Neither the first two harmonics nor the large-band noise are attributed to wake interactions.

Fournier, Francette; Roger, Michel

1989-03-01

295

Prediction of jet mean flow structure in support of HSCT noise suppression concepts  

NASA Astrophysics Data System (ADS)

The paper describes the application of techniques based on computational fluid dynamics to the simulation of jet flowfields. A solution code for the Reynolds-averaged Navier-Stokes equations is supplemented by conventional two-equation turbulence models based on the Boussinesq approximation. The axisymmetric SCIPVIS code is enhanced with the PARCH and CRAFT codes to examine plug-jet flowfields and imperfectly expanded axisymmetric free round jets. The sensitivity of shock/boundary layer interactions is observed in simulations of the plug case, and the adaptive gridding in the disk region and turbulence levels generated at the triple point are identified as areas in the Mach case that require improvement. Jet-wave structure in the region beyond the first several shock cells can be predicted, and turbulence modeling can be undertaken with respect to improving compressibility, length scale, vorticity, and energy budget. The mean flow structure of imperfectly expanded jets can be studied to develop related noise suppression concepts for the High-Speed Civilian Transport (HSCT).

Sinha, N.; Dash, S. M.; York, B. J.; Lee, R. A.

1991-06-01

296

Broadband optical cosite interference cancellation  

NASA Astrophysics Data System (ADS)

Here, we provide an overview of broadband cosite interference reduction using an optical system to perform incoherent counter-phase modulation and subtraction. The equation governing interference cancellation depth is derived and discussed with respect to two key parameters, attenuation and delay accuracy. Cancellation depth is then examined with respect to signal bandwidth and device parameters to provide a context for predicted cancellation performance. Experimentally recorded interference cancellation data is presented along with predicted performance to show the agreement of theory and data.

Bruno, Jonathan; Lu, Maddie; Deng, Yanhua; Prucnal, Paul

2013-05-01

297

A model suitable for predicting the noise associated with the ducted tail rotor of a helicopter  

NASA Astrophysics Data System (ADS)

Different fenestron configurations are studied experimentally. The measured acoustical characteristics include frequency spectra and directivity for several pitch angles of the rotor blades. The primary noise sources discussed include the rotor noise due to ingestion of preturbulence, the stator noise due to interaction with rotor created viscous wakes, and the noise due to the presence of transmission shaft and support arm in the stator. A method is developed to take into account the wakes and the potential field. Good agreement is found between experiment and theory.

Fournier, Francette

298

A Novel Broadband Ultrasonic Location System  

Microsoft Academic Search

Indoor ultrasonic location systems provide ne-grained position data to ubiquitous computing applications. However, the ultrasonic location systems previously developed utilize narrowband transducers, and thus perform poorly in the presence of noise and are constrained by the fact that signal collisions must be avoided. In this paper, we present a novel ultrasonic location system which uti- lizes broadband transducers. We describe

Mike Hazas; Andy Ward

2002-01-01

299

Measuring Broadband's Economic Impact.  

National Technical Information Service (NTIS)

Does broadband Internet access matter to the U.S. economy. Given how recently broadband has been adopted, little empirical research has investigated its economic impact. The analysis presented in this report represents a first attempt to measure the impac...

C. A. Osorio M. A. Sirbu S. E. Gillett W. H. Lehr

2006-01-01

300

Theoretical predictions for the effect of nebular emission on the broad-band photometry of high-redshift galaxies  

NASA Astrophysics Data System (ADS)

By combining optical and near-IR observations from the Hubble Space Telescope with near-IR photometry from the Spitzer Space Telescope, it is possible to measure the rest-frame UV-optical colours of galaxies at z = 4-8. The UV-optical spectral energy distribution of star formation dominated galaxies is the result of several different factors. These include the joint distribution of stellar masses, ages and metallicities (solely responsible for the pure stellar spectral energy distribution), and the subsequent reprocessing by dust and gas in the interstellar medium. Using a large cosmological hydrodynamical simulation (MassiveBlack-II), we investigate the predicted spectral energy distributions of galaxies at high redshift with a particular emphasis on assessing the potential contribution of nebular emission. We find that the average (median) pure stellar UV-optical colour correlates with both luminosity and redshift such that galaxies at lower redshift and higher luminosity are typically redder. Assuming that the escape fraction of ionizing photons is close to zero, the effect of nebular emission is to redden the UV-optical 1500 - Vw colour by, on average, 0.4 mag at z = 8 declining to 0.25 mag at z = 4. Young and low-metallicity stellar populations, which typically have bluer pure stellar UV-optical colours, produce larger ionizing luminosities and are thus more strongly affected by the reddening effects of nebular emission. This causes the distribution of 1500 - Vw colours to narrow and the trends with luminosity and redshift to weaken. The strong effect of nebular emission leaves observed-frame colours critically sensitive to the redshift of the source. For example, increasing the redshift by 0.1 can result in observed-frame colours changing by up to ˜0.6. These predictions reinforce the need to include nebular emission when modelling the spectral energy distributions of galaxies at high redshift and also highlight the difficultly in interpreting the observed colours of individual galaxies without precise redshift information.

Wilkins, Stephen M.; Coulton, William; Caruana, Joseph; Croft, Rupert; Matteo, Tiziana Di; Khandai, Nishikanta; Feng, Yu; Bunker, Andrew; Elbert, Holly

2013-09-01

301

Theoretical predictions for the effect of nebular emission on the broad-band photometry of high-redshift galaxies  

NASA Astrophysics Data System (ADS)

By combining optical and near-IR observations from the Hubble Space Telescope with near-IR photometry from the Spitzer Space Telescope, it is possible to measure the rest-frame UV-optical colours of galaxies at z = 4-8. The UV-optical spectral energy distribution of star formation dominated galaxies is the result of several different factors. These include the joint distribution of stellar masses, ages and metallicities (solely responsible for the pure stellar spectral energy distribution), and the subsequent reprocessing by dust and gas in the interstellar medium. Using a large cosmological hydrodynamical simulation (MassiveBlack-II), we investigate the predicted spectral energy distributions of galaxies at high redshift with a particular emphasis on assessing the potential contribution of nebular emission. We find that the average (median) pure stellar UV-optical colour correlates with both luminosity and redshift such that galaxies at lower redshift and higher luminosity are typically redder. Assuming that the escape fraction of ionizing photons is close to zero, the effect of nebular emission is to redden the UV-optical 1500 - Vw colour by, on average, 0.4 mag at z = 8 declining to 0.25 mag at z = 4. Young and low-metallicity stellar populations, which typically have bluer pure stellar UV-optical colours, produce larger ionizing luminosities and are thus more strongly affected by the reddening effects of nebular emission. This causes the distribution of 1500 - Vw colours to narrow and the trends with luminosity and redshift to weaken. The strong effect of nebular emission leaves observed-frame colours critically sensitive to the redshift of the source. For example, increasing the redshift by 0.1 can result in observed-frame colours changing by up to ˜0.6. These predictions reinforce the need to include nebular emission when modelling the spectral energy distributions of galaxies at high redshift and also highlight the difficultly in interpreting the observed colours of individual galaxies without precise redshift information.

Wilkins, Stephen M.; Coulton, William; Caruana, Joseph; Croft, Rupert; Matteo, Tiziana Di; Khandai, Nishikanta; Feng, Yu; Bunker, Andrew; Elbert, Holly

2013-11-01

302

Application of LMS adaptive predictive filtering for muscle artifact (noise) cancellation from EEG signals  

Microsoft Academic Search

The presence of muscle artifact (noise) affects the electroencephalograph (EEG) analysis. This paper deals with the filtering of the muscle artifact (noise) from a muscle artifact contaminated EEG, by a hybrid approach. In this, the muscle artifact component outside the EEG band is removed by lowpass filtering and the component within the EEG band by the least mean square gradient

S. V. Narasimhan; D. Narayana Dutt

1996-01-01

303

A model for predicting propagation of anthropogenic acoustic noise in the sea  

Microsoft Academic Search

There is a growing environmental concern about the effect high level anthropogenic acoustic signals and noise can have on the life in sea in general, also noise in the form of transients signal generated by air guns used in marine seismic exploration. The signals from such air guns have the potential to travel to far distances and cause annoyance, discomfort

Camilla Broch Pedersen; Jens M. Hovem; Hefeng Dong

2005-01-01

304

Measurement and prediction of noise from low-altitude military aircraft operations  

Microsoft Academic Search

In response to the rapid growth in demand for information on noise levels around military airfields in the UK, NPL developed AIRNOISE, a mathematical model for computing aircraft noise contours. Since its first applications in 1981, the model has been used to determine zones of eligibility within the MoD compensation scheme. The model has been subject to continuous development, e.g.,

Bernard F. Barry; Richard C. Payne; Anthony L. Harris; Ralph J. Weston

1992-01-01

305

A Preliminary Axial Fan Design Method with the Considerat ion of Performance and Noise Characteristics  

NASA Astrophysics Data System (ADS)

Presented in this paper are a fan's aero-acoustic performance method and its computation procedure which combines aerodynamic flow field data, performances and noise levels of fan. The internal flow field and the performance of fan are analyzed by the through-flow modeling, inviscid pitch-averaged quasi-3D flow analysis combined with flow deviation and pressure loss distribution models. Based on the predicted internal flow field dada by the trough-flow modeling, fan noise is predicted by two models for the discrete frequency noise due to rotating steady aerodynamic thrust and blade interaction and for the broadband noise due to turbulent boundary layer and wake vortex shedding. The present predictions of the flow distribution, the performance and the noise level of fan are well agreed with actual test results.

Lee, Chan; Kil, Hyun Gwon

2010-06-01

306

Rotorcraft noise: Status and recent developments  

Microsoft Academic Search

This paper briefly reviews rotorcraft noise mechanisms and their approximate importance for different types of rotorcraft in different flight regimes. Discrete noise is due to periodic flow disturbances and includes impulsive noise produced by phenomena which occur during a limited segment of a blade's rotation. Broadband noise results when rotors interact with random disturbances, such as turbulence, which can originate

Albert R. George; Ben Wel-C. Sim; David R. Polak

1993-01-01

307

A prediction model for the vortex shedding noise from the wake of an airfoil or axial flow fan blades  

NASA Astrophysics Data System (ADS)

An analytical model is presented for predicting the vortex shedding noise generated from the wake of axial flow fan blades. The downstream wake of a fan blade is assumed to be dominated by the von Karman vortex street, and the strength and the shedding frequency of the wake vortex are determined from the wake structure model. The fluctuating pressure and lift on the blade surface, which are induced from the vortices in the wake, are analyzed by incorporating the wake model for the von Karman vortex street with thin airfoil theory. The predicted vortex shedding frequency and the overall sound pressure level compare favorably with the measured results for the vortex shedding noise from axial flow fans.

Lee, C.; Chung, M. K.; Kim, Y.-H.

1993-06-01

308

Predicting temporary threshold shifts in a bottlenose dolphin (Tursiops truncatus): the effects of noise level and duration.  

PubMed

Noise levels in the ocean are increasing and are expected to affect marine mammals. To examine the auditory effects of noise on odontocetes, a bottlenose dolphin (Tursiops truncatus) was exposed to octave-band noise (4-8 kHz) of varying durations (<2-30 min) and sound pressures (130-178 dB re 1 microPa). Temporary threshold shift (TTS) occurrence was quantified in an effort to (i) determine the sound exposure levels (SELs) (dB re 1 microPa(2) s) that induce TTS and (ii) develop a model to predict TTS onset. Hearing thresholds were measured using auditory evoked potentials. If SEL was kept constant, significant shifts were induced by longer duration exposures but not for shorter exposures. Higher SELs were required to induce shifts in shorter duration exposures. The results did not support an equal-energy model to predict TTS onset. Rather, a logarithmic algorithm, which increased in sound energy as exposure duration decreased, was a better predictor of TTS. Recovery to baseline hearing thresholds was also logarithmic (approximately -1.8 dB/doubling of time) but indicated variability including faster recovery rates after greater shifts and longer recoveries necessary after longer duration exposures. The data reflected the complexity of TTS in mammals that should be taken into account when predicting odontocete TTS. PMID:19275338

Mooney, T Aran; Nachtigall, Paul E; Breese, Marlee; Vlachos, Stephanie; Au, Whitlow W L

2009-03-01

309

Impact of Noise and Seasonality on the Detection and Nonlinear Prediction of Chaos From Finite River-Flow Time Series  

NASA Astrophysics Data System (ADS)

Detection of possible chaos in hydrological time series can be useful for scientific understanding of the component processes as well as for short-term predictability and predictive modeling. However, the presence of noise and seasonality makes the detection of any nonlinear component, especially chaos, difficult in finite time series. This study utilizes approaches such as correlation dimension (CD), phase space reconstruction (PSR) and artificial neural networks (ANN) for the detection of possible chaos. The results on simulated data generated from the Lorenz system of equations (contaminated with various levels of noise and periodicity) indicate the presence of thresholds in terms of "noise to chaotic-signal" and "seasonality to chaotic-signal", beyond which the currently available set of tools are unable to detect the chaotic component. The simulation results also demonstrate that the underlying chaotic or nonlinear component, if present, may be extractable from a time series contaminated with noise and seasonality. We also show the impacts on predictive modeling, for example we illustrate the possibility that a decomposition of the time series observations into periodic, nonlinear dynamical and noise components can be utilized to improve predictive modeling through a best fit strategy that applies the most suitable methodology to each component. Analysis of monthly streamflow data from the Arkansas River at Little Rock and daily streamflow data from the Colorado River below Parker dam shows that the chaotic component can be detected in the Arkansas data but not in the Colorado data. The extracted chaotic component from the Arkansas data is processed further to generate multi-step ahead predictions. These results suggest that while chaos may be detectable in certain hydrological time series leading in many situations to improved short-term predictability, not all hydrological time series exhibits detectable chaos. Acknowledgment: Auroop R Ganguly gratefully acknowledges the Laboratory Directed Research and Development Program (SEED money funds) of the Oak Ridge National Laboratory (ORNL), managed by UT-Battelle, LLC for the U.S. DOE under Contract No. DE-AC05-00OR22725.

Ganguly, A. R.; Khan, S.; Saigal, S.

2005-12-01

310

Behavioral Responses of Gray Whales to Industrial Noise: Feeding Observations and Predictive Modeling,  

National Technical Information Service (NTIS)

An investigation was made of the potential effects of underwater noise from petroleum industry activities on feeding gray whales. The investigation consisted of two components, a field study and an acoustic model study. The field study was performed near ...

C. I. Malme B. Wuersig J. E. Bird P. Tyack

1986-01-01

311

Underwater radiated noise from modern commercial ships.  

PubMed

Underwater radiated noise measurements for seven types of modern commercial ships during normal operating conditions are presented. Calibrated acoustic data (<1000 Hz) from an autonomous seafloor-mounted acoustic recorder were combined with ship passage information from the Automatic Identification System. This approach allowed for detailed measurements (i.e., source level, sound exposure level, and transmission range) on ships of opportunity. A key result was different acoustic levels and spectral shapes observed from different ship-types. A 54 kGT container ship had the highest broadband source level at 188 dB re 1 ?Pa@1m; a 26 kGT chemical tanker had the lowest at 177 dB re 1 ?Pa@1m. Bulk carriers had higher source levels near 100 Hz, while container ship and tanker noise was predominantly below 40 Hz. Simple models to predict source levels of modern merchant ships as a group from particular ship characteristics (e.g., length, gross tonnage, and speed) were not possible given individual ship-type differences. Furthermore, ship noise was observed to radiate asymmetrically. Stern aspect noise levels are 5 to 10 dB higher than bow aspect noise levels. Collectively, these results emphasize the importance of including modern ship-types in quantifying shipping noise for predictive models of global, regional, and local marine environments. PMID:22280574

McKenna, Megan F; Ross, Donald; Wiggins, Sean M; Hildebrand, John A

2012-01-01

312

A prediction method of the acoustical properties of multilayered noise control materials in standing wave-duct systems  

NASA Astrophysics Data System (ADS)

A new experimental approach, herein referred to as hybrid multilayer prediction, for evaluating acoustical properties of multilayered treatments of noise control materials, such as the absorption ratio and transmission loss, is presented. The two-cavity and two-load methods (TLMs) were performed in a special standing wave duct with two configurations of two- and four-microphone holders. By referring to theoretical expressions and standard approaches, such as the standing wave ratio method from the literature, The validity of these two methods for measuring the transfer matrix was investigated, and some empirical conditions of using limits for the two-cavity and TLMs, based on great amounts of experimental data, were put forth. Based on the total four-pole transfer matrices calculated by combining the two-cavity method and the TLM, some prediction examples for a set of multilayered material treatments were conducted. The prediction results suggest that the newly proposed hybrid prediction method is feasible and effective and that it can be used directly to predict the acoustical properties of an exceedingly thick sample or a multilayer treatment consisting of variable materials. In view of engineering applications, the method may be used for optimizing the in situ designs of multilayered material systems or other noise-control configurations, such as automotive mufflers.

Lee, C.-M.; Wang, Y. S.

2006-11-01

313

A Fresh Look At 'Broadband' Passive Sonar Processing  

Microsoft Academic Search

Traditional passive broadband sonar processing has been constructed by performing spatial decomposition (beamforming) followed by a temporal filter ( Eckart weighting) structured to maximize deflection for signal present while minimizing deflection under noise only conditions. This processing, while approaching optimality in the stationary single signal-stationary noise case, is not well suited for clutter rich environments and spectrally diverse signal sets.

Robert E. Zarnich

314

Noncausal f–x–y regularized nonstationary prediction filtering for random noise attenuation on 3D seismic data  

NASA Astrophysics Data System (ADS)

Seismic noise attenuation is very important for seismic data analysis and interpretation, especially for 3D seismic data. In this paper, we propose a novel method for 3D seismic random noise attenuation by applying noncausal regularized nonstationary autoregression (NRNA) in f–x–y domain. The proposed method, 3D NRNA (f–x–y domain) is the extended version of 2D NRNA (f–x domain). f–x–y NRNA can adaptively estimate seismic events of which slopes vary in 3D space. The key idea of this paper is to consider that the central trace can be predicted by all around this trace from all directions in 3D seismic cube, while the 2D f–x NRNA just considers that the middle trace can be predicted by adjacent traces along one space direction. 3D f–x–y NRNA uses more information from circumjacent traces than 2D f–x NRNA to estimate signals. Shaping regularization technology guarantees that the nonstationary autoregression problem can be realizable in mathematics with high computational efficiency. Synthetic and field data examples demonstrate that, compared with f–x NRNA method, f–x–y NRNA can be more effective in suppressing random noise and improve trace-by-trace consistency, which are useful in conjunction with interactive interpretation and auto-picking tools such as automatic event tracking.

Liu, Guochang; Chen, Xiaohong

2013-06-01

315

Air Force procedure for predicting aircraft noise around airbases: Airbase operations program (BASEOPS) description  

NASA Astrophysics Data System (ADS)

A user manual is presented for the BASEOPS 3.00 program developed by AAMRL/BBE. The installation, use and limitations of this program is described. BASEOPS is the menu driven computerized airbase operations input program used in doing airbase noise assessments under the USAF Air Installation Compatible Use Zone (AICUZ) program. BASEOPS will create a file that can be directly interfaced to the NOISEMAP 6.0 program, used to calculate the total noise exposure from these input operations. BASEOPS contains default performance profiles (takeoff and landing) for Military Transient and Civil aircraft. The program also allows the user to create a NOISEMAP input file for any subset of the input data through a Global Editing Menu. This can be used for quickly creating multiple noise analyses for different operational input scenarios.

Lee, Robert A.; Mohlman, Henry T.

1990-01-01

316

High speed propeller performance and noise predictions at takeoff/landing conditions  

NASA Astrophysics Data System (ADS)

The performance and noise of a high speed SR-7A model propeller under takeoff/landing conditions are considered. The blade loading distributions are obtained by solving the three-dimensional Euler equations and the sound pressure levels are computed using a time domain approach. At the nominal takeoff operating point, the blade sections near the hub are lightly or negatively loaded. The chordwise loading distributions are distinctly different from those of cruise conditions. The noise of the SR-7A model propeller at takeoff is dominated by the loading noise, similar to that at cruise conditions. The waveforms of the acoustic pressure signature are nearly sinusoidal in the plane of the propeller. The computed directivity of the blade passing frequency tone agrees fairly well with the data at nominal takeoff blade angle.

Nallasamy, M.; Woodward, R. P.; Groeneweg, J. F.

1987-01-01

317

High speed propeller performance and noise predictions at takeoff/landing conditions  

NASA Astrophysics Data System (ADS)

The performance and noise of a high speed SR-7A model propeller under takeoff/landing conditions are considered. The blade loading distributions are obtained by solving the three-dimensional Euler equations and the sound pressure levels are computed using a time domain approach. At the nominal takeoff operating point, the blade sections near the hub are lightly or negatively loaded. The chordwise loading distributions are distinctly different from those of cruise conditions. The noise of the SR-7A model propeller at takeoff is dominated by the loading noise, similar to that at cruise conditions. The waveforms of the acoustic pressure signature are nearly sinusoidal in the plane of the propeller. The computed directivity of the blade passing frequency tone agrees fairly well with the data at nominal takeoff blade angle.

Nallasamy, M.; Woodward, R. P.; Groeneweg, J. F.

1988-01-01

318

A prediction method for separating and quantifying noise contributions from casings and other plate like components in complex machines  

NASA Astrophysics Data System (ADS)

In the context of noise source identification in machines, sound intensity, pressure or velocity distributions on a plane in space are commonly provided by intensity or holography maps. These maps, however, are not capable of separating the sources that are located on different planes, e.g. machines' radiating casings versus internal noise sources. The method discussed in this paper has been developed to analyze such situations. It consists of multiple partially coherent inputs-single output modeling to predict the radiations generated by machine casings or other plate like components. A parallel analysis with intensity will then enable to separate the casing or plate contribution from those of the internal sources. The application of this technique must, however, be accompanied by tools that allow to check its validity. Several of such tools are suggested. The method applications and validity checks have been discussed for a grinder wheel guard and a panel saw's blade casing.

Nejade, A.

2012-11-01

319

A Study on Discrete Frequency Noise Generated by Interaction between the Wake of a Centrifugal Impeller and a Cylinder (2nd Report; Prediction of the Interaction Noise)  

Microsoft Academic Search

In the first report, in order to clarify the influence of the cutoff of the scroll casing on the discrete frequency noise, the dependence of the diameter of a cylinder on the discrete frequency noise generated from interaction with the wake of a centrifugal impeller was discussed. From results of the analysis on the interaction noise and flow around the

Soichi SASAKI; Hidechito HAYASHI

320

Aspects of startling noises  

Microsoft Academic Search

In a pilot study, aspects of startling noises were investigated. For a typical synthetic broadband sound, i.e. uniform exciting noise, the influence of the following stimulus parameters on startling reactions were studied: (1) Magnitude of a level increase (5...40 dB, 10ms rise time) above a pedestal of 45 dB (2) Level increase of 30 dB for pedestals between 40 and

Hugo Fastl; Stefan Kerber; Nikolaus Guzsvány

321

Prediction of acoustic scattering in the time domain and its applications to rotorcraft noise  

Microsoft Academic Search

This work aims at the development of a numerical method for the analysis of acoustic scattering in the time domain and its applications to rotorcraft noise. This purpose is achieved by developing two independent methods: (1) an analytical formulation of the pressure gradient for an arbitrary moving source and (2) a time-domain moving equivalent source method. First, the analytical formulation

Seongkyu Lee

2009-01-01

322

Prediction of Work Efficiency in Early Adolescence under the Effects of Noise  

ERIC Educational Resources Information Center

|This is a short summary of research on how different stress factors in the work environment (climate, light, noise) affect work performance of early adolescents. Due to the complexity of the measurements, the research consisted of a small sample of male adolescents (N = 20); average age 13.5 years (SD = 0.25). Tasks were used which demanded…

Fosnaric, Samo; Planinsec, Jurij

2008-01-01

323

Development of hybrid method for the prediction of underwater propeller noise  

Microsoft Academic Search

Noise reduction and control is an important problem in the performance of underwater acoustic systems and in the habitability of the passenger ship for crew and passenger. Furthermore, sound generated by a propeller is critical in underwater detection and it is often related to the survivability of the vessel especially for military purpose. This paper presents a numerical study on

Hanshin Seol; Jung-Chun Suh; Soogab Lee

2005-01-01

324

Time Series Prediction Model of Soil Moisture Based on Wavelet DeNoising  

Microsoft Academic Search

Soil moisture is one of the most important factors which affect crop yields directly. In recent years, although upland field area increased not too much, agricultural water resources utilization increased which has led to a waste of water resources in Sanjiang Plain. In order to solve the above problem, wavelet de-noising theory and time series analysis are adopted to analyze

Peng Shengmin; Li Tianxiao; Wang Fulin

2009-01-01

325

The importance of quadrupole sources in prediction of transonic tip speed propeller noise  

Microsoft Academic Search

A theoretical analysis is presented for the harmonic noise of high speed, open rotors. Far field acoustic radiation equations based on the Ffowcs-Williams\\/Hawkings theory are derived for a static rotor with thin blades and zero lift. Near the plane of rotation, the dominant sources are the volume displacement and the rho U(2) quadrupole, where u is the disturbance velocity component

D. B. Hanson; M. R. Fink

1978-01-01

326

EMI conducted emission in the differential mode emanating from an SCR: phenomena and noise level prediction  

Microsoft Academic Search

This paper deals with an EMC analysis of a power converter. In particular, the phenomena and modeling of conducted noise emission caused by an SCR (silicon controlled rectifier) are described. Theoretical results in the time as well as frequency domain are discussed and compared to the time signal measured and its spectrum

R. Scheich; J. Roudet

1995-01-01

327

Active noise control by using prediction of time series data with a neural network  

Microsoft Academic Search

To extend applications of an active noise control system, it is required to reduce the distance from the detection microphone to the error microphone. The reduced distance is needed because of the delays of the system. Although it can be changed by hardware improvements, there is a limit to the amount by which the system can be shortened. The purpose

T. Matsuura; T. Hiei; H. Itoh; K. Torikoshi

1995-01-01

328

The importance of quadrupole sources in prediction of transonic tip speed propeller noise  

Microsoft Academic Search

A theoretical analysis is presented for the harmonic noise of high speed, open rotors. Far field acoustic radiation equations based on the Ffowcs Williams\\/Hawkings theory are derived for a static rotor with thin blades and zero lift. Near the plane of rotation, the dominant sources are the volume displacement and the varrhou2 quadrupole, where u is the disturbance velocity component

D. B. Hanson; M. R. Fink

1979-01-01

329

Suppress noise output of YIG-tuned sources  

Microsoft Academic Search

The design of drive circuits aimed to reduce the noise output of YIG-tuned oscillators is presented. The noise reduction technique is illustrated by analysis of a low-noise electronically tunable oscillator in a spectrum analyzer. A variety of noise types (thermal, broadband operational amplifier, and popcorn noise) are evaluated, and measures to avoid the harmful constituents at each stage of the

R. Bales

1980-01-01

330

Algorithms based on theoretical models for design multilayer structures for acoustic isolation to air noise prediction  

NASA Astrophysics Data System (ADS)

In this Ph.D. work we wanted to obtain theoretical models to simulate different configurations used in the field of acoustic noise isolation, to take into account, as far as possible, the internal resonant effect of the air chamber that exists among the layers and moreover the effect that produces the pass of finite to infinite layers. For this reason we selected models that helped us to get the maximum information of the multilayer configuration i.e. displacement of the plates, reflected and transmitted pressure, and the pressure wave generated in the inner air chambers or in the proper absorbent material bulk. In this work we achieved two main contributions: firstly we proposed different methods to be allows characterise acoustically many absorbers and impermeable layers, second we tested and validated different models to characterise multilayer structures, that allow isolation against air noise.

Alba Fernandez, Jesus

331

The Broadband Buzz.  

ERIC Educational Resources Information Center

|"Broadband," the term for a variety of high-speed Internet options, opens up many opportunities for online classroom learning. Challenges for school districts include keeping the network running, training teachers, and paying for it. A sidebar lists broadband resources. (MLF)|

Buchanan, Bruce

2003-01-01

332

Supersonic Jet Noise Reduction  

NASA Astrophysics Data System (ADS)

Three noise reduction technologies have been examined experimentally as they have been applied to overexpanded, perfectly expanded and underexpanded supersonic jets from convergent-divergent nozzles. The technologies include chevrons, fluidic injection and fluidically enhanced chevrons. The flowfield was measured by shadowgraph and particle image velocimetry (PIV). The acoustics were measured by near and far-field microphone. Chevrons were shown to reduce or eliminate screech, reduce broadband shock associated noise and reduce mixing noise. Fluidic injection was shown to reduce screech, reduce broadband shock associated noise and mixing noise. It also shifts the shock-associated noise peaks to higher frequency and generates increased high frequency noise as chevrons do. The fluidic injection produces the same reduction near x/D = 10 at mid frequencies and the same increase in high frequencies near the nozzle as chevrons. Both noise reduction techniques reduce the size of the large scale structures and so both reduce BBSN by the same mechanism. The principal difference between chevrons and fluidic injection is that for constant injection mass flow the effectiveness of fluidic injection increases with decreasing values of Mj while for chevrons the trend is reversed.

Gutmark, Ephraim; Heeb, Nick; Liu, Junhui; Kailasanath, Kailas

2011-11-01

333

Noise Reduction Of Air Blower Casing Using Composites  

Microsoft Academic Search

Sound subjectively, what is heard by the ear; objectively, is a mecha nical disturbance from equilibrium in an elastic medium.\\u000a The noise produced by a rotating component has two main components, the broadband noise and the discrete frequency noise.\\u000a The broadband noise from a rotor is due to random loading forces on the blades, which are induced by the absorption

Y. Anil Kumar; S. Rajesh

334

Error Evaluation for the Broadband Interferometry  

NASA Astrophysics Data System (ADS)

Two-dimensional and three-dimensional VHF source mapping emitted by lightning discharge progression have been established by a unique technique based on the broadband interferometry. Though the functions and potential capabilities of the broadband interferometry have been shown widely, the discussion on their accuracy have not been discussed sufficiently yet. Then the objective of this paper is presenting the quantitative discussion and evidence of the superiority of the broadband Interferometer. The main attention is paid on the two-dimensional source localization for VHF impulses. One unit of interferometer consists of three antennas, and azimuth and elevation of VHF sources against the site of the interferometer can be derived. Since the background noise components are superimposed on the VHF pulse signals intrinsically, the calculated azimuth and elevation include location error. The broadband interferometry is based on the phase estimation for more than a hundred Fourier components. Since the Fourier component is linearly independent each other, we can estimate the azimuth and elevation for all Fourier components. If there is no noise, and if there is no dispersions during VHF pulse propagation, the azimuth and elevation for all Fourier components should be the same. In the real observations it does not happen, and estimated azimuth and elevation vary depending on the frequency. The variation of azimuth and elevation depends on the original VHF pulse, and in some cases there is less variation and other cases the variation are large. In any cases we normally adopt the arithmetic averaging or weighted averaging to finalize the azimuth and elevation for VHF pulse source. If we think about this situation seriously, we can notice the existence of the redundancy in terms of the Fourier spectra. This means that we can reach an idea to use this for the discussion of location error or ambiguity of the broadband interferometry. One additional idea is the application of broadcast signals. The frequency bandwidth of the broadband interferometry is ranging from 25 MHz to 250MHz, and this frequency band includes FM radio and VHF TV services. Since the relative positions of broadcasts against the VHF broadband interferometer are constant, and the azimuth of Fourier frequency component corresponding to the broadcast is known. It is able for us to use this to calibrate the broadband system, and it can be done on site exactly on real time.

MORIMOTO, T.; KAWASAKI, Z.; MARDIANA, R.

2001-12-01

335

Dual broadband USED CARS  

NASA Astrophysics Data System (ADS)

An easily implemented laser beam arrangement for dual broadband CARS is demonstrated which should facilitate the utilization of CARS for simultaneous measurement of a multiplicity of constituents. In this arrangement, all wave-mixing combinations are three-dimensionally phase matched and each pump component participates in a three-color wave-mixing sequence. The laser beam arrangement for dual broadband USED (unstable resonator spatially enhanced detection) CARS is also presented along with simultaneously generated dual broadband CARS signatures from CO2, N2, and H2O in the postflame zone of a premixed C2H4-air flame.

Eckbreth, A. C.; Anderson, T. J.

1986-05-01

336

Improved prediction of the turbulence-shear contribution to wind noise pressure spectra.  

PubMed

In previous research [Raspet et al., J. Acoust. Soc. Am. 123(3), 1260-1269 (2008)], predictions of the low frequency turbulence-turbulence and turbulence-mean shear interaction pressure spectra measured by a large wind screen were developed and compared to the spectra measured using large spherical wind screens in the flow. The predictions and measurements agreed well except at very low frequencies where the turbulence-mean shear contribution dominated the turbulence-turbulence interaction pressure. In this region the predicted turbulence-mean shear interaction pressure did not show consistent agreement with microphone measurements. The predicted levels were often much larger than the measured results. This paper applies methods developed to predict the turbulence-shear interaction pressure measured at the ground [Yu et al., J. Acoust. Soc. Am. 129(2), 622-632 (2011)] to improve the prediction of the turbulence-shear interaction pressure above the ground surface by incorporating a realistic wind velocity profile and realistic turbulence anisotropy. The revised prediction of the turbulence-shear interaction pressure spectra compares favorably with wind-screen microphone measurements in large wind screens at low frequency. PMID:22225016

Yu, Jiao; Raspet, Richard; Webster, Jeremy; Abbott, JohnPaul

2011-12-01

337

Broadband synthetic aperture geoacoustic inversion.  

PubMed

A typical geoacoustic inversion procedure involves powerful source transmissions received on a large-aperture receiver array. A more practical approach is to use a single moving source and/or receiver in a low signal to noise ratio (SNR) setting. This paper uses single-receiver, broadband, frequency coherent matched-field inversion and exploits coherently repeated transmissions to improve estimation of the geoacoustic parameters. The long observation time creates a synthetic aperture due to relative source-receiver motion. This approach is illustrated by studying the transmission of multiple linear frequency modulated (LFM) pulses which results in a multi-tonal comb spectrum that is Doppler sensitive. To correlate well with the measured field across a receiver trajectory and to incorporate transmission from a source trajectory, waveguide Doppler and normal mode theory is applied. The method is demonstrated with low SNR, 100-900?Hz LFM pulse data from the Shallow Water 2006 experiment. PMID:23862809

Tan, Bien Aik; Gerstoft, Peter; Yardim, Caglar; Hodgkiss, William S

2013-07-01

338

Interior Noise Predictions in the Preliminary Design of the Large Civil Tiltrotor (LCTR2).  

National Technical Information Service (NTIS)

A prediction scheme was established to compute sound pressure levels in the interior of a simplified cabin model of the second generation Large Civil Tiltrotor (LCTR2) during cruise conditions, while being excited by turbulent boundary layer flow over the...

D. D. Boyd F. W. Grosveld R. H. Cabell

2013-01-01

339

A series solution to smoothing, filtering, and prediction problems involving correlated signal and noise (Corresp.)  

Microsoft Academic Search

A recently presented series solution to smoothing, filtering, and prediction problems is extended to include correlation between the white and colored components of the observations, as required in applications to feedback communications and feedback control.

W. Gardner

1975-01-01

340

Evaluation of Ride Quality Prediction Methods for Helicopter Interior Noise and Vibration Environments.  

National Technical Information Service (NTIS)

This paper presents the results of a simulator study conducted to compare and validate various ride quality prediction methods for use in assessing passenger/crew ride comfort within helicopters. Included are results quantifying 35 helicopter pilots' disc...

J. D. Leatherwood S. A. Clevenson D. D. Hollenbaugh

1984-01-01

341

Relationship between container ship underwater noise levels and ship design, operational and oceanographic conditions  

PubMed Central

Low-frequency ocean ambient noise is dominated by noise from commercial ships, yet understanding how individual ships contribute deserves further investigation. This study develops and evaluates statistical models of container ship noise in relation to design characteristics, operational conditions, and oceanographic settings. Five-hundred ship passages and nineteen covariates were used to build generalized additive models. Opportunistic acoustic measurements of ships transiting offshore California were collected using seafloor acoustic recorders. A 5–10?dB range in broadband source level was found for ships depending on the transit conditions. For a ship recorded multiple times traveling at different speeds, cumulative noise was lowest at 8?knots, 65% reduction in operational speed. Models with highest predictive power, in order of selection, included ship speed, size, and time of year. Uncertainty in source depth and propagation affected model fit. These results provide insight on the conditions that produce higher levels of underwater noise from container ships.

McKenna, Megan F.; Wiggins, Sean M.; Hildebrand, John A.

2013-01-01

342

Relationship between container ship underwater noise levels and ship design, operational and oceanographic conditions  

NASA Astrophysics Data System (ADS)

Low-frequency ocean ambient noise is dominated by noise from commercial ships, yet understanding how individual ships contribute deserves further investigation. This study develops and evaluates statistical models of container ship noise in relation to design characteristics, operational conditions, and oceanographic settings. Five-hundred ship passages and nineteen covariates were used to build generalized additive models. Opportunistic acoustic measurements of ships transiting offshore California were collected using seafloor acoustic recorders. A 5-10 dB range in broadband source level was found for ships depending on the transit conditions. For a ship recorded multiple times traveling at different speeds, cumulative noise was lowest at 8 knots, 65% reduction in operational speed. Models with highest predictive power, in order of selection, included ship speed, size, and time of year. Uncertainty in source depth and propagation affected model fit. These results provide insight on the conditions that produce higher levels of underwater noise from container ships.

McKenna, Megan F.; Wiggins, Sean M.; Hildebrand, John A.

2013-05-01

343

Broadband Thermoplastic Radomes.  

National Technical Information Service (NTIS)

Radomes requiring frequency coverage from S through K band present a difficult design challenge. Past experience with broadband antenna systems has shown that a low fines ratio A sandwich radome offers the best electrical performance. However, a blunt A s...

K. Hollenbeck M. Rehrl

1984-01-01

344

Broadband Accelerator Control Network.  

National Technical Information Service (NTIS)

A broadband data communications network has been implemented at BNL for control of the Alternating Gradient Synchrotron (AG) proton accelerator, using commercial CATV hardware, dual coaxial cables as the communications medium, and spanning 2.0 km. A 4 MHz...

J. Skelly T. Clifford R. Frankel

1983-01-01

345

Predicting the Inflow Distortion Tone Noise of the NASA Glenn Advanced Noise Control Fan with a Combined Quadrupole-Dipole Model.  

National Technical Information Service (NTIS)

A combined quadrupole-dipole model of fan inflow distortion tone noise has been extended to calculate tone sound power levels generated by obstructions arranged in circumferentially asymmetric locations upstream of a rotor. Trends in calculated sound powe...

L. D. Koch

2012-01-01

346

Rotor noise in maneuvering flight  

Microsoft Academic Search

The objective of this research is to understand the physics of rotor noise in the maneuvering flight. To achieve this objective, an integrated noise prediction system is constructed, namely GenHel-MFW-PSU-WOPWOP. This noise prediction system includes a flight simulation code, a high fidelity free vortex-wake code, and a rotor acoustic prediction code. By using this noise prediction system, rotor maneuver noise

Hsuan-Nien Chen

2006-01-01

347

Noise and Noise Sickness.  

National Technical Information Service (NTIS)

Basic concepts and questions about noise, which contribute to a proper understanding of the characteristic of industrial noise as well as an experimental acoustical complex for the study of the noise factor, are examined. Special attention has been given ...

Y. T. Andreyevagalanina S. V. Alekeseyev A. V. Kadyskin G. A. Suvopov

1973-01-01

348

Ocean acoustic noise and passive coherent array processing  

NASA Astrophysics Data System (ADS)

Broadband correlation processing for extracting time-domain Green's functions and coherent wavefronts from random ocean noise has been demonstrated recently using experiments and numerical simulations that are consistent with theoretical predictions. Ocean acoustic noise processing presents additional challenges over its seismological counterpart. Mainly, the ocean environment is temporally non-stationary and it is spatially heterogeneous. Further, in the lower underwater acoustic frequency regime of about 20 to 500 Hz, space-time episodic shipping is the dominant noise source. The data from different publications and research groups are gathered here, with the goal being to review recent underwater acoustic research that demonstrates the viability and potential applications of passive coherent array processing in the ocean.

Roux, Philippe; Kuperman, W. A.; Sabra, Karim G.

2011-09-01

349

75 FR 6627 - Broadband Technology Opportunities Program  

Federal Register 2010, 2011, 2012, 2013

...Broadband Technology Opportunities Program AGENCY: National...for the Broadband Opportunities Program (BTOP) published...Broadband Technology Opportunities Program (BTOP) established pursuant to the American Recovery and...

2010-02-10

350

Rectification of different-color noise  

NASA Astrophysics Data System (ADS)

The approach for generating a broad-band colored noise is proposed, which allows the transition between ``red'' and ``green'' noise. The rectification of the noise with different colors characterized by the net current of a Brownian particle moving in a ratchet-like potential is studied by using the digital simulation. The present noise is also compared with the harmonic noise. The results show that the average current reverses sign when the external noise is filtered off in the region of low frequencies to a sufficient extent. Finally, a parameter plane of the noise with the numerically estimated line of the current reversal is plotted.

Bao, Jing-Dong

1999-06-01

351

Improving differential detection of MDPSK by nonlinear noise prediction and sequence estimation  

Microsoft Academic Search

A new technique is proposed to improve the performance of differential detection (DD) of M-ary differential phase-shift keying (MDPSK) significantly, applying sequence estimation. In order to obtain an appropriate representation of the received signal, a nonlinear time-variant finite impulse response or infinite impulse response prediction-error filter is used. For both filter structures the optimum coefficients are derived, assuming transmission over

Robert Schober; Wolfgang H. Gerstacker; Johannes B. Huber

1999-01-01

352

A wall-mounted source array for the excitation of incoherent broadband sound fields with prescribed modal distributions in ducts  

NASA Astrophysics Data System (ADS)

In the analysis of broadband sound fields in ducts, for example, turbofan engines, large exhaust stacks, and exhaust mufflers, the assumption of ‘Equal Energy per Mode’ (EEpM) is frequently made. The practical realization of such a sound fields is valuable as a means of, for example, allowing liner attenuation measurements obtained from measurements on different test rigs to be compared directly, or for allowing measurements results to be compared with computer predictions in which the assumption is made. This paper describes a technique in which arrays of sound sources at the wall of a duct are driven by white noise signals to generate a sound field of prescribed modal energy distribution and modal coherence. The number of sources required for effective mode synthesis and the source geometry are also discussed. An example is presented in which ‘EEpM’ broadband sound field is generated up to a maximum non-dimensional frequency of ka=20 using 152 sources.

Jeong, Wontae; Lee, Soogab; Joseph, P.

2006-02-01

353

Recent results about fan noise: Its generation, radiation and suppression  

NASA Astrophysics Data System (ADS)

Fan noise including its generation, radiation characteristics, and suppression by acoustic treatment is studied. In fan noise generation, results from engine and fan experiments, using inflow control measures to suppress noise sources related to inflow distortion and turbulence, are described. The suppression of sources related to inflow allows the experiments to focus on the fan or engine internal sources. Some of the experiments incorporated pressure sensors on the fan blades to sample the flow disturbances encountered by the blades. From these data some inferences can be drawn about the origins of the disturbances. Also, hot wire measurements of a fan rotor wake field are presented and related to the fan's noise signature. The radiation and the suppression of fan noise are dependent on the acoustic modes generated by the fan. Fan noise suppression and radiation is described by relating these phenomena to the mode cutoff ratio parameter. In addition to its utility in acoustic treatment design and performance prediction, cutoff ratio was useful in developing a simple description of the radiation pattern for broadband fan noise. Some of the findings using the cutoff ratio parameter are presented.

Feiler, C. E.

354

Effect of broadband-noise masking on the behavioral response of a harbor porpoise (Phocoena phocoena) to 1-s duration 6-7 kHz sonar up-sweeps.  

PubMed

Naval sonar systems produce signals which may affect the behavior of harbor porpoises, though their effect may be reduced by ambient noise. To show how natural ambient noise influences the effect of sonar sweeps on porpoises, a porpoise in a pool was exposed to 1-s duration up-sweeps, similar in frequency range (6-7 kHz) to those of existing naval sonar systems. The sweep signals had randomly generated sweep intervals of 3-7 s (duty cycle: 19%). Behavioral parameters during exposure to signals were compared to those during baseline periods. The sessions were conducted under five background noise conditions: the local normal ambient noise and four conditions mimicking the spectra for wind-generated noise at Sea States 2-8. In all conditions, the sweeps caused the porpoise to swim further away from the transducer, surface more often, swim faster, and breathe more forcefully than during the baseline periods. However, the higher the background noise level, the smaller the effects of the sweeps on the surfacing behavior of the porpoise. Therefore, the effects of naval sonar systems on harbor porpoises are determined not only by the received level of the signals and the hearing sensitivity of the animals but also by the background noise. PMID:21476686

Kastelein, Ronald A; Steen, Nele; de Jong, Christ; Wensveen, Paul J; Verboom, Willem C

2011-04-01

355

Real-Scale Measurement Results for Audible Noise from AC Overhead Transmission Lines and Prediction Formula in Heavy Rain  

Microsoft Academic Search

The audible noise produced by corona discharge from AC overhead transmission line conductors is one of the major factors affecting the design of conductors, particularly for transmission lines with voltages above 500 kV. The audible noise has two components, which are random noise with frequency components from several hundreds to 20 kHz and pure tones with a power line frequency

Kazuo Tanabe

2009-01-01

356

Predicting auditory tone-in-noise detection performance: the effects of neural variability.  

PubMed

Collecting and analyzing psychophysical data is a fundamental mechanism for the study of auditory processing. However, because this approach relies on human listening experiments, it can be costly in terms of time and money spent gathering the data. The development of a theoretical, model-based procedure capable of accurately predicting psychophysical behavior could alleviate these issues by enabling researchers to rapidly evaluate hypotheses prior to conducting experiments. This approach may also provide additional insight into auditory processing by establishing a link between psychophysical behavior and physiology. Signal detection theory has previously been combined with an auditory model to generate theoretical predictions of psychophysical behavior. Commonly, the ideal processor outperforms human subjects. In order for this model-based technique to enhance the study of auditory processing, discrepancies must be eliminated or explained. In this paper, we investigate the possibility that neural variability, which results from the randomness inherent in auditory nerve fiber responses, may explain some of the previously observed discrepancies. In addition, we study the impact of combining information across nerve fibers and investigate several models of multiple-fiber signal processing. Our findings suggest that neural variability can account for much, but not all, of the discrepancy between theoretical and experimental data. PMID:14765701

Huettel, Lisa G; Collins, Leslie M

2004-02-01

357

Predicting noise-induced hearing loss in human populations. The contribution of the ISO-1999 and ANSI S3.44 standards  

NASA Astrophysics Data System (ADS)

This paper reviews the ISO-1999 and ANSI S3.44 standards and the literature related to prediction of noise-induced hearing loss (NIHL) in humans. The dearth of contemporary population-based studies of hearing loss among industrial, low noise-exposed individuals have made the ISO-1999 and ANSI S3.44 standards a key source of comparative data for assessing the risk of NIHL. This paper will highlight how these standards have been used in several published papers to examine the magnitude of NIHL risk, predictions of noise-induced thresholds in hearing conservation data, and to generate hypotheses regarding the biologic plausibility of hearing loss due to chemicals or other ototoxic agents.

Prince, Mary M.

2003-04-01

358

Broadband homodecoupled heteronuclear multiple bond correlation spectroscopy.  

PubMed

A general concept for removing proton-proton scalar J couplings in 2D NMR spectroscopy is proposed. The idea is based on introducing an additional J resolved dimension into the pulse sequence of a conventional 2D experiment to design a pseudo 3D NMR experiment. The practical demonstration is exemplified on the widely used gradient coherence selected heteronuclear long-range correlation spectroscopy (HMBC). We refer to this type of pulse sequence as tilt HMBC experiment. For every (13)C chemical shift evolution increment, a homonuclear J resolved experiment is recorded. The long-range defocusing delay of the HMBC pulse sequence is exploited to implement this building block. The J resolved evolution period is incremented in a way very similar to ACCORDION spectroscopy to accommodate the buildup of heteronuclear long-range antiphase magnetisation as well. After Fourier transformation in all dimensions the spectra are tilted in the J resolved dimension. Finally, a projection along the J resolved dimension is calculated leading to almost disappearance of proton-proton spin multiplicities in the 2D tilt HMBC spectrum. The tilt HMBC experiment combines sensitivity with simple experimental setup and can be recorded with short recycle delays, when combined with Ernst angle excitation. The recorded spectra display singlet proton signals for long-range correlation peaks making an unambiguous signal assignment much easier. In addition to the new experiment a simple processing technique is applied to efficiently suppress the noise originating from forward linear prediction in the indirect evolution dimensions. In case of issues with fast repetition times, probe heating and RF power handling most of the RF pulses can be replaced by broadband, frequency swept pulses operating at much lower power. PMID:23395829

Sakhaii, Peyman; Haase, Burkhard; Bermel, Wolfgang

2013-01-08

359

Method and apparatus for recording broad-band seismic data  

SciTech Connect

A receiver array for detecting seismic reflections is composed of geophones of several different natural frequencies divided into subarrays having lengths compatible with the natural frequencies of their geophones and the seismic wavelengths at the recording site. This system provides both frequency and spatial filtering at the sensors so as to enhance the signal-to-noise ratio of broad-band seismic signals.

Fix, J.E.; Crews, G.A.

1985-02-12

360

CNET: Broadband Regulation  

NSDL National Science Digital Library

In this article, staff writers for CNET, an online technology news source, discuss the "broadband war." The article focuses on a battle in Lafayette, La., over plans by BellSouth and cable provider Cox Communications to lay out their fiber-optic broadband network. The article provides a link to another article describing the "legal skirmish" from a year ago and goes on to discuss the issues surrounding the debate, which the authors say is essentially about "whether the government or private industries should take the leading role in building out what's considered this generation's critical infrastructure challenge."

361

The Case for Broadband Evangelism  

ERIC Educational Resources Information Center

|Higher education has an important stake in the national effort to widely deploy a state-of-the-art broadband public network. The Broadband Policy Group (BPG) developed a set of three principles to provide a consistent frame of reference for pursuing policy initiatives: (1) affordable broadband access; (2) a new regulatory structure; and (3)…

Augustson, J. Gary; Roberts, Mike

2004-01-01

362

The battle for broadband  

Microsoft Academic Search

Nobody likes it when Mommy and Daddy fight. Besides making everyone uncomfortable, it can be messy and costly, and, ultimately, everyone gets hurt. Which is exactly what may happen in the new battle over broadband. An intense, complex, and sprawling conflict is heating up between private telecommunications companies and municipalities throughout the U.S. over who can, or should, build out

Aaron Weiss

2005-01-01

363

Broadband Fixed Phase Shifters  

Microsoft Academic Search

Amethodtodesignplanarandcompactphaseshifters with broadband characteristics is presented. It utilizes broadside- coupled microstrip-coplanarwaveguide,andthustheproposed de- vices can be fabricated using the simple and cheap double-side printed circuit boards. The method is used to design 60 and 90 phase shifters. The simulated and measured results show that the developed phase shifters achieve 3 to 11 GHz bandwidth with low phase instability , very low

Amin M. Abbosh

2011-01-01

364

Broadband all-optical ultrasound transducers  

NASA Astrophysics Data System (ADS)

A broadband all-optical ultrasound transducer has been designed, fabricated, and tested for high-resolution ultrasound imaging. It consists of a two-dimensional gold nanostructure on a glass substrate, followed by a 3 ?m polydimethylsiloxane layer and a 30 nm gold layer. The signal to noise ratio of a pulse-echo signal is over 10 dB in the far field of the transducer, where the center frequency is 40 MHz with -6 dB bandwidth of 57 MHz. The potential for high-frequency ultrasound arrays using this technology is demonstrated using multiple measurements from the transducer to image a 25 ?m diameter wire.

Hou, Yang; Kim, Jin-Sung; Ashkenazi, Shai; Huang, Sheng-Wen; Guo, L. Jay; O'Donnell, Matthew

2007-08-01

365

Electroelastic modeling and experimental validations of piezoelectric energy harvesting from broadband random vibrations of cantilevered bimorphs  

NASA Astrophysics Data System (ADS)

We present electroelastic modeling, analytical and numerical solutions, and experimental validations of piezoelectric energy harvesting from broadband random vibrations. The modeling approach employed herein is based on a distributed-parameter electroelastic formulation to ensure that the effects of higher vibration modes are included, since broadband random vibrations, such as Gaussian white noise, might excite higher vibration modes. The goal is to predict the expected value of the power output and the mean-square shunted vibration response in terms of the given power spectral density (PSD) or time history of the random vibrational input. The analytical method is based on the PSD of random base excitation and distributed-parameter frequency response functions of the coupled voltage output and shunted vibration response. The first of the two numerical solution methods employs the Fourier series representation of the base acceleration history in an ordinary differential equation solver while the second method uses an Euler-Maruyama scheme to directly solve the resulting electroelastic stochastic differential equations. The analytical and numerical simulations are compared with several experiments for a brass-reinforced PZT-5H bimorph under different random excitation levels. The simulations exhibit very good agreement with the experimental measurements for a range of resistive electrical boundary conditions and input PSD levels. It is also shown that lightly damped higher vibration modes can alter the expected power curve under broadband random excitation. Therefore, the distributed-parameter modeling and solutions presented herein can be used as a more accurate alternative to the existing single-degree-of-freedom solutions for broadband random vibration energy harvesting.

Zhao, S.; Erturk, A.

2013-01-01

366

Broadband acoustooptic deflectors: new results.  

PubMed

A new broadband acoustooptic (AO) Bragg deflector using acoustic beam steering to track the Bragg angle is described. It features, instead of the conventional stepped array acoustic grating to produce the steering sound column, a flat transducer grating made from a single piezoelectric platelet bonded to the AO medium, with the spatially periodic phase variations created by interdigitating the electrode configuration. The advantage over the conventional stepped array, for deflectors operating at frequencies above 100 MHz, is the ease of fabrication of the device, an advantage that far outweighs its somewhat reduced acoustic power available for light diffraction. An analysis is presented to show that the achievable half-power bandwidth from beam steering deflectors under optimum design considerations is over four times the bandwidth of fixed beam deflectors having the same transducer dimensions. Experimental results on lead molybdate deflectors confirm the predicted fourfold improvement. PMID:20134855

Alphonse, G A

1975-01-01

367

Application of system engineering processes to analyze and predict engine cooling fan system noise for off-highway machines  

Microsoft Academic Search

System Engineering processes were applied to create a Cooling Fan System Noise Analysis Tool for a back-hoe loader machine. The Cooling Fan System Noise Analysis Tool combined elements of aeroacoustic theory, Fan Law, sound power measurements and particle image velocimetry into a single computer analysis tool. The cooling fan system consisted of a cooling fan, multiple radiators in front of

Christopher P. Masini; J. Adin Mann

2005-01-01

368

A vessel noise budget for Admiralty Inlet, Puget Sound, Washington (USA).  

PubMed

One calendar year of Automatic Identification System (AIS) ship-traffic data was paired with hydrophone recordings to assess ambient noise in northern Admiralty Inlet, Puget Sound, WA (USA) and to quantify the contribution of vessel traffic. The study region included inland waters of the Salish Sea within a 20 km radius of the hydrophone deployment site. Spectra and hourly, daily, and monthly ambient noise statistics for unweighted broadband (0.02-30 kHz) and marine mammal, or M-weighted, sound pressure levels showed variability driven largely by vessel traffic. Over the calendar year, 1363 unique AIS transmitting vessels were recorded, with at least one AIS transmitting vessel present in the study area 90% of the time. A vessel noise budget was calculated for all vessels equipped with AIS transponders. Cargo ships were the largest contributor to the vessel noise budget, followed by tugs and passenger vessels. A simple model to predict received levels at the site based on an incoherent summation of noise from different vessels resulted in a cumulative probability density function of broadband sound pressure levels that shows good agreement with 85% of the temporal data. PMID:23231102

Bassett, Christopher; Polagye, Brian; Holt, Marla; Thomson, Jim

2012-12-01

369

Characterizing residential broadband networks  

Microsoft Academic Search

A large and rapidly growing proportion of users connect to the Internet via residential broadband networks such as Dig- ital Subscriber Lines (DSL) and cable. Residential networks are often the bottleneck in the last mile of today's Internet. Their characteristics critically affect Internet applications, including voice-over-IP, online games, and peer-to-peer con- tent sharing\\/delivery systems. However, to date, few studies have

Marcel Dischinger; Andreas Haeberlen; P. Krishna Gummadi; Stefan Saroiu

2007-01-01

370

Roadmap to broadband ISDN  

Microsoft Academic Search

The two major emerging forms of ISDN (integrated services digital network), namely, narrowband and broadband (or B-ISDN), are contrasted. The authors note that although narrowband ISDN uses the technology of twisted pair loops, 64-Kb\\/s PCM (pulse-code modulation) circuit switches, and packet switches, B-ISDN will require fibre-optic links, digital cross connects, and optical switches; the probable network architecture of B-ISDN is

J. Ramasastry; K. S. Kim

1988-01-01

371

Study of noise transmission from an air compressor  

Microsoft Academic Search

The paper discusses the reduction of noise from a Porter Cable 4-gal, 135-psi air compressor. The objectives were to identify the major sources of noise, implement possible noise control measures, and evaluate their effectiveness. Sound measurements were taken according to a procedure that was developed and based on the standards for power tools. Broadband analysis (1\\/12 octave band) was done

Subhro Nathak; Anand Puranik; Jeffrey Schut; Lee Wells; M. D. Rao

2005-01-01

372

Comparing prediction power and stability of broadband and hyperspectral vegetation indices for estimation of green leaf area index and canopy chlorophyll density  

Microsoft Academic Search

Hyperspectral reflectance data representing a wide range of canopies were simulated using the combined PROSPECT+SAIL model. The simulations were used to study the stability of recently proposed vegetation indices (VIs) derived from adjacent narrowband spectral reflectance data across the visible (VIS) and near infrared (NIR) region of the electromagnetic spectrum. The prediction power of these indices with respect to green

N. h. Broge; E. Leblanc

2001-01-01

373

On the global EMC aspect of broadband power line communications using the “HF” frequency band  

Microsoft Academic Search

Measurement data and computer modelling is used to assess the potential of global cumulative radio interference effects caused by over the horizon ionospheric propagation of unwanted emissions from broadband power line communications (PLC) systems operating in the HF band (1-30 MHz). A comparison of the results with the ITU-R atmospheric radio noise atlas indicates that the present natural noise levels

H. Widmer

2000-01-01

374

Practical Ranges of Loudness Levels of Various Types of Environmental Noise, Including Traffic Noise, Aircraft Noise, and Industrial Noise  

PubMed Central

In environmental noise control one commonly employs the A-weighted sound level as an approximate measure of the effect of noise on people. A measure that is more closely related to direct human perception of noise is the loudness level. At constant A-weighted sound level, the loudness level of a noise signal varies considerably with the shape of the frequency spectrum of the noise signal. In particular the bandwidth of the spectrum has a large effect on the loudness level, due to the effect of critical bands in the human hearing system. The low-frequency content of the spectrum also has an effect on the loudness level. In this note the relation between loudness level and A-weighted sound level is analyzed for various environmental noise spectra, including spectra of traffic noise, aircraft noise, and industrial noise. From loudness levels calculated for these environmental noise spectra, diagrams are constructed that show the relation between loudness level, A-weighted sound level, and shape of the spectrum. The diagrams show that the upper limits of the loudness level for broadband environmental noise spectra are about 20 to 40 phon higher than the lower limits for narrowband spectra, which correspond to the loudness levels of pure tones. The diagrams are useful for assessing limitations and potential improvements of environmental noise control methods and policy based on A-weighted sound levels.

Salomons, Erik M.; Janssen, Sabine A.

2011-01-01

375

Assessment and evaluation of noise controls on roof bolting equipment and a method for predicting sound pressure levels in underground coal mining  

NASA Astrophysics Data System (ADS)

Over-exposure to noise remains a widespread and serious health hazard in the U.S. mining industries despite 25 years of regulation. Every day, 80% of the nation's miners go to work in an environment where the time weighted average (TWA) noise level exceeds 85 dBA and more than 25% of the miners are exposed to a TWA noise level that exceeds 90 dBA, the permissible exposure limit (PEL). Additionally, MSHA coal noise sample data collected from 2000 to 2002 show that 65% of the equipment whose operators exceeded 100% noise dosage comprise only seven different types of machines; auger miners, bulldozers, continuous miners, front end loaders, roof bolters, shuttle cars (electric), and trucks. In addition, the MSHA data indicate that the roof bolter is third among all the equipment and second among equipment in underground coal whose operators exceed 100% dosage. A research program was implemented to: (1) determine, characterize and to measure sound power levels radiated by a roof bolting machine during differing drilling configurations (thrust, rotational speed, penetration rate, etc.) and utilizing differing types of drilling methods in high compressive strength rock media (>20,000 psi). The research approach characterized the sound power level results from laboratory testing and provided the mining industry with empirical data relative to utilizing differing noise control technologies (drilling configurations and types of drilling methods) in reducing sound power level emissions on a roof bolting machine; (2) distinguish and correlate the empirical data into one, statistically valid, equation, in which, provided the mining industry with a tool to predict overall sound power levels of a roof bolting machine given any type of drilling configuration and drilling method utilized in industry; (3) provided the mining industry with several approaches to predict or determine sound pressure levels in an underground coal mine utilizing laboratory test results from a roof bolting machine and (4) described a method for determining an operators' noise dosage of a roof bolting machine utilizing predicted or determined sound pressure levels.

Matetic, Rudy J.

376

Noise and noise abatement in fans and blowers: A review  

Microsoft Academic Search

Noise generation and its reduction industrial fans (ventilators) is addressed. A review is given of the fan types commonly in use and their practical applications, the mechanisms of the aerodynamic noise generation in fans, theoretical and empirical prediction methods for fan noise, acoustic similarity laws, and noise reduction methods by means of the fan construction and fan operation. Measurement procedures

W. Neise

1980-01-01

377

Broadband Signal Enhancement of Seismic Array Data: Application to Long-Period Surface Waves and High-Frequency Wavefields.  

National Technical Information Service (NTIS)

The original main goals of this project were twofold: (1) development of new techniques for enhancement of low signal to noise surface wave signals recorded by broadband arrays, and (2) research on fundamental properties of high-frequency wavefields. Two ...

G. L. Pavlis

1998-01-01

378

Experimental investigation of an inversion technique for the determination of broadband duct mode amplitudes by the use of near-field sensor arrays.  

PubMed

This paper is an experimental investigation of an inverse technique for deducing the amplitudes of the modes radiated from a turbofan engine, including schemes for stablizing the solution. The detection of broadband modes generated by a laboratory-scaled fan inlet is performed using a near-field array of microphones arranged in a geodesic geometry. This array geometry is shown to allow a robust and accurate modal inversion. The sound power radiated from the fan inlet and the coherence function between different modal amplitudes are also presented. The knowledge of such modal content is useful in helping to characterize the source mechanisms of fan broadband noise generation, for determining the most appropriate mode distribution model for duct liner predictions, and for making sound power measurements of the radiated sound field. PMID:17672635

Castres, Fabrice O; Joseph, Phillip F

2007-08-01

379

Build broadband multilayer multiplexers  

NASA Astrophysics Data System (ADS)

Multiplexers provide a way of subdividing a wide frequency-band signal into different narrowband signals and are key components in multicarrier microwave satellite-communications systems. The design and construction of multiple-octave multiplexers is described and a systematic design approach for producing matched broadband multiplexers is discussed. Attention is given to the use of hybrid directional couplers, lowpass filters, bandpass filters, and diplexers in the construction of multiplexers. A step-by-step approach for the design of multiplexers is given.

Ghannouchi, Fadhel M.; Beauregard, Francois; Gouere, Francois; Toutain, Serge

1993-05-01

380

A method of multi-channel reference signals acquiring in broadband ANC  

Microsoft Academic Search

In a flank array on an unmanned underwater vehicle (UUV), self-generated noise which has broadband and colored spectrum property\\u000a in frequency and spatial domain is the main factor affecting the performance of weak signal detection, so the technique of\\u000a adaptive noise cancellation (ANC) as well as physical denoising and active noise cancellation are often used in practice.\\u000a Because ANC is

Ling-Kun Ma; Jian-Guo Huang; Li-Jie Zhang

2008-01-01

381

Broadband Internet's Value for Rural America  

Microsoft Academic Search

As broadband—or high-speed—Internet use has spread, Internet applications requiring high transmission speeds have become an integral part of the “Information Economy,” raising concerns about those who lack broadband access. This report analyzes (1) rural broadband use by consumers, the community-at-large, and businesses; (2) rural broadband availability; and (3) broadband’s social and economic effects on rural areas. It also summarizes results

Peter L. Stenberg; Mitchell J. Morehart; Stephen J. Vogel; John Cromartie; Vincent E. Breneman; Dennis M. Brown

2009-01-01

382

Environmental issues: noise, rail noise, and high-speed rail  

Microsoft Academic Search

The six papers in the report deal with the following areas: the effect of noise barriers on the market value of adjacent residential properties; control of airport- and aircraft-related noise in the United States; a traffic-assignment model to reduce noise annoyance in urban networks; a survey of railroad occupational noise sources; a prediction procedure for rail transportation ground-borne noise and

F. L. Hall; J. D. Welland; C. R. Bragdon; J. W. Houtman; B. H. Immers

1987-01-01

383

Environmental issues: noise, rail noise, and high-speed rail  

SciTech Connect

The six papers in the report deal with the following areas: the effect of noise barriers on the market value of adjacent residential properties; control of airport- and aircraft-related noise in the United States; a traffic-assignment model to reduce noise annoyance in urban networks; a survey of railroad occupational noise sources; a prediction procedure for rail transportation ground-borne noise and vibration; and high-speed rail in California: the dream, the process, and the reality.

Hall, F.L.; Welland, J.D.; Bragdon, C.R.; Houtman, J.W.; Immers, B.H.

1987-01-01

384

Wireless performance improvement using an embedded balanced dipole antenna in laptop computer considering platform noise impact  

Microsoft Academic Search

Balanced antenna was proposed to improve the wireless communication performance by reducing platform noise. The concept was implemented and demonstrated using a balanced antenna design and ceramic balun. Platform noise reduction was achieved up to 5 dB and 11 dB for broadband noise and narrowband noise respectively. It is promising to improve the throughput and range by employing the balanced

Seong-Youp Suh; V. K. Nair; A. Konanur; U. Karacaoglu; Kwan-ho Lee

2008-01-01

385

Fiber-optic gyroscopes with broad-band sources  

Microsoft Academic Search

The use of broad-band sources, polarized and unpolarized, in fiber gyroscopes with linearly birefringent fibers, is studied theoretically. Polarization-mode coupling in the fiber is modeled using one-mode coupling center. Gyroscope output equations are obtained which are useful in interpreting an origin of fiber noise in the limiting cases of low and high fiber birefringence. Interference effects in the output are

W. K. Burns; Chin-Lin Chen; R. Moeller

1983-01-01

386

RIN-suppressed ultralow noise interferometric fiber optic gyroscopes (IFOGs) for improving inertial stabilization of space telescopes  

NASA Astrophysics Data System (ADS)

Pointing, acquisition, and tracking (PAT) systems in spaceborne optical communications terminals can exploit inertial sensors and actuators to counter platform vibrations and maintain steady beam pointing. Interferometric fiber optic gyroscopes (IFOGs) can provide sensitive angle rate measurements down to very low (sub-milliHertz) mechanical frequencies, potentially reducing the required beacon power and facilitating acquisition for a spaceborne optical communications terminals. Incoherent broadband light sources are used in IFOGs to alleviate detrimental effects of optical nonlinearities, backscattering, and polarization non-reciprocity. But incoherent broadband sources have excess noise or relative intensity noise (RIN), caused by the beating of different spectral components on the photodetector. Unless RIN noise is suppressed, IFOG performance cannot be improved once the light on the photodetector exceeds one photon per coherence time (~microWatts). We propose a simple method to dramatically suppress the RIN of an incoherent light source and thereby reduce the angle random walk (ARW) of an IFOG using such a source. We demonstrate 20 dB RIN suppression of a broadband EDFA source, which we predict could improve the angle random walk (ARW) of an IFOG using this source by 12 dB.

Hakimi, Farhad; Moores, John D.

2013-03-01

387

Analysis of a simplified normalized covariance measure based on binary weighting functions for predicting the intelligibility of noise-suppressed speech  

PubMed Central

The normalized covariance measure (NCM) has been shown previously to predict reliably the intelligibility of noise-suppressed speech containing non-linear distortions. This study analyzes a simplified NCM measure that requires only a small number of bands (not necessarily contiguous) and uses simple binary (1 or 0) weighting functions. The rationale behind the use of a small number of bands is to account for the fact that the spectral information contained in contiguous or nearby bands is correlated and redundant. The modified NCM measure was evaluated with speech intelligibility scores obtained by normal-hearing listeners in 72 noisy conditions involving noise-suppressed speech corrupted by four different types of maskers (car, babble, train, and street interferences). High correlation (r = 0.8) was obtained with the modified NCM measure even when only one band was used. Further analysis revealed a masker-specific pattern of correlations when only one band was used, and bands with low correlation signified the corresponding envelopes that have been severely distorted by the noise-suppression algorithm and?or the masker. Correlation improved to r = 0.84 when only two disjoint bands (centered at 325 and 1874 Hz) were used. Even further improvements in correlation (r = 0.85) were obtained when three or four lower-frequency (<700 Hz) bands were selected.

Chen, Fei; Loizou, Philipos C.

2010-01-01

388

Evaluation of annoyance from low frequency noise under laboratory conditions.  

PubMed

The aim of the study was to investigate the annoyance of low frequency noise (LFN) at levels normally prevailing at workplaces in control rooms and office-like areas. Two different laboratory experiments were carried out. The first experiment included 55 young volunteers and the second one comprised 70 older volunteers, categorized in terms of sensitivity to noise. The subjects listened to noise samples with different spectra, including LFNs at sound pressure level (SPL) of 45-67 dBA, and evaluated annoyance using a 100-score graphical rating scale. The subjective ratings of annoyance were compared to different noise metrics. In both the experiments, there were no differences in annoyance assessments between females and males. A significant influence of individual sensitivity to noise on annoyance rating was observed for some LFNs. Annoyance of LFN was not rated higher than annoyance from broadband noises without or with less prominent low frequencies at similar A-weighted SPLs. In both the experiments, median annoyance rating of LFN highly correlated with A-weighted SPL (L(Aeq,T)), low frequency A-weighted SPL (L(LFAeq,T)) and C-weighted SPL (L(Ceq,T)). However, it is only the two latter noise metrics (i.e. L(LFAeq,T) and L(Ceq,T)) which seem to be reliable predictors of annoyance exclusively from LFN. The young and older participants assessed similar annoyance from LFN at similar L(LFAeq,T) or L(Ceq,T) levels. Generally, over half of the subjects were predicted to be highly annoyed by LFN at the low frequency A-weighted SPL or C-weighted SPL above 62 and 83 dB, respectively. PMID:20603573

Pawlaczyk-Luszczynska, Malgorzata; Dudarewicz, Adam; Szymczak, Wieslaw; Sliwinska-Kowalska, Mariola

389

Noise emission levels in coal industry  

Microsoft Academic Search

The noise levels in coal washeries, coal preparation plants, open cast and underground mining centres are very high when compared to accepted limits for occupational noise exposure. Even the residual noise level when there is minimal activity is 80 to 82 dB. The results of the noise emitted by machines are analysed to predict an overall noise climate.

O. Sharma; V. Mohanan; M. Singh

1998-01-01

390

Areawide Road Traffic Noise Contour Maps  

Microsoft Academic Search

In this study a framework for developing an object-oriented tool -DRONE (areawide Dynamic ROad traffic NoisE simulator) to generate areawide noise contour maps for a road network is demonstrated. This provides faster access to information for abatement of noise policies. The approach for integrating the dynamic output from traffic simulator to noise model, which predicts traffic noise based on geographical

Ashish Bhaskar; Edward Chung; Masao Kuwahara; Yasuo Oshino

391

Broadband reconfigurable optical beam-forming systems  

NASA Astrophysics Data System (ADS)

It is shown that by applying spatial frequency dependent optical phase compensation in an optical heterodyne process, variable RF delay can be achieved over a prescribed frequency band. Experimental results that demonstrate the performance of the delay line with regard to both maximum delay and resolution over a broad bandwidth are presented. Additionally, a spatially integrated optical system is proposed for control of phased array antennas, providing mechanical stability, essentially eliminating the drift problems associated with free-space optical systems, and providing high packing density. This approach uses a class of SLM known as a deformable mirror device and leads to a steerable arbitrary antenna radiation pattern of the true time-delay type. Also considered is the ability to utilize the delay line as a general photonic signal processing element in an adaptive (reconfigurable) transversal frequency filter configuration. Such systems are widely applicable in jammer/noise canceling systems, broadband ISDN, spread spectrum secure communications and the like.

Toughlian, Edward N.; Zmuda, Henry; Carter, Charity A.

1994-06-01

392

Seismic Noise Study Based on Markov and Extended Self-Smilarity Analysis  

NASA Astrophysics Data System (ADS)

We propose a novel method for analysing back-ground seismic noise data before an earthquake by using Markov Time Scale algorithm to predict large earthquakes.Alert time obtained based on the data from broad-band stations by analyzing 200 earthquakes with magnitude grater than 4.5, that occurred in Iran , between January 1 and December 30, 2009. The numerical coefficients for each area will be estimated from the data collected for the area. The Markov Time Scale algorithm analysis can be extended to all the stations around the world.

Allameh Zadeh, Mostafa

2010-05-01

393

Word Identification in Noise.  

ERIC Educational Resources Information Center

|Notes that speech intelligibility has traditionally been measured by presenting words mixed in noise to listeners for identification at different signal-to-noise ratios. The words are produced in isolation or in sequence contexts where the predictability of specific items can be varied. Emphasizes that the technique provides valuable data about…

Pisoni, David B.

1996-01-01

394

Single-Carrier Layered Space-Frequency Equalization with Time Domain Noise-Prediction for MIMO Systems  

NASA Astrophysics Data System (ADS)

Error-propagation is an important issue and should be carefully coped with in the decision-feedback equalizers (DFE). Ignoring the impact of error-propagation often leads to impractical laboratory results. In this paper, we investigate two novel layered space-frequency equalizers (LSFE) for single-carrier multiple-input multiple-output (MIMO) systems, where the recently proposed frequency-domain equalizer with time domain noise-predictor (FDE-NP) is adopted at each stage of the LSFE. We first derive the partially-connected LSFE with noise predictor (PC-LSFE-NP) which has exactly the same mean square error (MSE) as the conventional LSFE under the assumption of perfect feedback. However, if error-propagation is considered, the proposed PC-LSFE-NP can achieve better performance than the conventional LSFE due to the more reliable feedback output by the decoders. To reduce the interference from the not yet detected layers in the feedback section, we then introduce the fully-connected LSFE with noise predictor (FC-LSFE-NP), in which all layers are implicitly equalized within each stage and their decisions fed back internally. The powerful feedback filter of FC-LSFE-NP brings significant performance superiority over the conventional LSFE and PC-LSFE-NP with either perfect or imperfect feedback. Moreover, we propose a simple soft-demapper for the equalizers to avoid information loss during decoding, and thus, further improve the performance. Finally, we compare the performance of (PC/FC)-LSFE-NP with the existing schemes by computer simulations.

Feng, Ang; Yin, Qinye; Ding, Le

395

Broadband beamspace DOA estimation algorithms  

Microsoft Academic Search

Two kinds of broadband beamspace high-resolution DOA estimation algorithms are studied in this paper. The first one is broadband beamspace coherent high-resolution processing method based on constant beamwidth beamformers. In this method, conventional narrowband beamspace high-resolution DOA estimation methods such as beamspace MUSIC can be applied to the output of constant beamwidth beamformers. Because of the fixed beamformers used in

Yixin Yang; Chum Wan; Chao Sun

2003-01-01

396

A Novel Broadband Active Balun  

Microsoft Academic Search

We have developed a novel broadband active balun. It consists of series-connected common-gate FETs and a common-source FET. The active balun achieved broadband characteristics by using series-connected common-gate FETs with the same gradient as the phase performance of the common-source FET. From 500 MHz to more than 10 GHz, the fabricated active balun shows a phase error of less than

Munenari Kawashima; Tadao Nakagawa; Katsuhiko Araki

2003-01-01

397

Broadband Communications: The Commercial Impact  

Microsoft Academic Search

The impact of broadband ISDN (integrated services digital network) is assessed. It is pointed out that the key step in its introduction, i.e. the replacement of the copper wire infrastructure by optical fiber, is already taking place. Two alternative routes for the introduction of broadband services are described: the market-driven route and the investment-led route. The market-driven route entails carriers

Stephen Timms

1989-01-01

398

Protective broadband window coatings  

NASA Astrophysics Data System (ADS)

Optical windows employed in current and future airborne and ground based optical sensor systems are required to provide long service life under extreme environmental conditions including blowing sand and high speed rain. State of the art sensor systems are employing common aperture windows which must provide optical bandpasses from the TV to the LWIR. Operation Desert Storm experience indicates that current optical coatings provide limited environmental protection which adversely affects window life cycle cost. Most of these production coatings also have limited optical bandpasses (LWIR, MWIR, or TV-NIR). A family of optical coatings has been developed which provide a significant increase in rain and sand impact protection to current optical window materials. These coatings can also be tailored to provide either narrow optical bandwidth (e.g., LWIR) or broadband transmittance (TV- LWIR). They have been applied to a number of standard optical window materials. These coating have successfully completed airborne rain and sand abrasion test with minimal impact on optical window performance. Test results are presented. Low cost service life is anticipated as well as the ability to operate windows in even more taxing environments than currently feasible.

Askinazi, Joel; Narayanan, Authi A.

1997-06-01

399

Broadband Transmission EPR Spectroscopy  

PubMed Central

EPR spectroscopy employs a resonator operating at a single microwave frequency and phase-sensitive detection using modulation of the magnetic field. The X-band spectrometer is the general standard with a frequency in the 9–10 GHz range. Most (bio)molecular EPR spectra are determined by a combination of the frequency-dependent electronic Zeeman interaction and a number of frequency-independent interactions, notably, electron spin – nuclear spin interactions and electron spin – electron spin interactions, and unambiguous analysis requires data collection at different frequencies. Extant and long-standing practice is to use a different spectrometer for each frequency. We explore the alternative of replacing the narrow-band source plus single-mode resonator with a continuously tunable microwave source plus a non-resonant coaxial transmission cell in an unmodulated external field. Our source is an arbitrary wave digital signal generator producing an amplitude-modulated sinusoidal microwave in combination with a broadband amplifier for 0.8–2.7 GHz. Theory is developed for coaxial transmission with EPR detection as a function of cell dimensions and materials. We explore examples of a doublet system, a high-spin system, and an integer-spin system. Long, straigth, helical, and helico-toroidal cells are developed and tested with dilute aqueous solutions of spin label hydroxy-tempo. A detection limit of circa 5 µM HO-tempo in water at 800 MHz is obtained for the present setup, and possibilities for future improvement are discussed.

Hagen, Wilfred R.

2013-01-01

400

Broadband accelerator control network  

SciTech Connect

A broadband data communications network has been implemented at BNL for control of the Alternating Gradient Synchrotron (AG) proton accelerator, using commercial CATV hardware, dual coaxial cables as the communications medium, and spanning 2.0 km. A 4 MHz bandwidth Digital Control channel using CSMA-CA protocol is provided for digital data transmission, with 8 access nodes available over the length of the RELWAY. Each node consists of an rf modem and a microprocessor-based store-and-forward message handler which interfaces the RELWAY to a branch line implemented in GPIB. A gateway to the RELWAY control channel for the (preexisting) AGS Computerized Accelerator Operating system has been constructed using an LSI-11/23 microprocessor as a device in a GPIB branch line. A multilayer communications protocol has been defined for the Digital Control Channel, based on the ISO Open Systems Interconnect layered model, and a RELWAY Device Language defined as the required universal language for device control on this channel.

Skelly, J.; Clifford, T.; Frankel, R.

1983-01-01

401

Heterogeneous broadband network  

NASA Astrophysics Data System (ADS)

Although the vision for the future Integrated Broadband Communication Network (IBCN) is an all optical network, it is certain that for a long period to come, the network will remain very heterogeneous, with a mixture of different physical media (fiber, coax and twisted pair), transmission systems (PDH, SDH, ADSL) and transport protocols (TCP/IP, AAL/ATM, frame relay). In the current work towards the IBCN, the ATM concept is considered the generic network protocol for both public and private network, with the ability to use different underlying transmission protocols and, through adaptation protocols, provide the appropriate services (old as well as new) to the customer. One of the major difficulties of heterogeneous network is the restriction that is usually given by the lowest common denominator, e.g. in terms of single channel capacity. A possible way to overcome these limitations is by extending the ATM concept with a multilink capability, that allows us to use separate resources as one common. The improved flexibility obtained by this protocol extension further allows a real time optimization of network and call configuration, without any impact on the quality of service seen from the user. This paper describes an example of an ATM based multilink protocol that has been experimentally implemented within the RACE project 'STRATOSPHERIC'. The paper outlines the complexity of introducing an extra network functionality compared with the added value, such as an improved ability to recover an error due to a malfunctioning network component.

Dittmann, Lars

1995-11-01

402

Aeroacoustic investigation on the noise from ultralight aircraft  

NASA Astrophysics Data System (ADS)

Flyover and ground/static noise measurements as well as wind tunnel tests on individual propellers of ultralight aircraft led to the identification of the essential noise sources and to recommendations for noise reduction. For undisturbed inflow conditions (tractor propellers) and blade tip Mach numbers below 0.5 the resulting propeller noise is of broadband nature, while above that limit discrete-frequency rotational-noise sources dominate. Additional sources occur with pusher-propeller configurations as a consequence of the disturbed inflow. It is demonstrated that ground/static noise measurements are not suitable for certification testing.

Dahlen, Helmut; Dobrzynski, Werner; Heller, Hanno

1987-08-01

403

In Situ Performance of Paroscientific Digiquartz Broadband Pressure Sensors  

NASA Astrophysics Data System (ADS)

Since the first installation of a CORK at hole 857D (Middle Valley, Juan de Fuca Ridge) in 1991 Paroscientific Digiquartz Broadband Pressure sensors have played a key role in monitoring formation and seafloor pressures at CORK installations. Both pressure measurements provide information about the hydrological and seismological processes at time scales from seconds to years. Therefore sensor in situ performance e.g. effective resolution and long-term stability needed to be evaluated. Starting with the installation of the NOAA tsunami early warning system DART in 1983, the Paroscientific Digiquartz Broadband Depth Sensor has been deployed for long-term ocean bottom pressure measurements in numerous marine investigations. The sensor turned out to be very reliable with very good accuracy within a broad measuring range and an extremely high resolution at deep sea ambient pressures. However, up to now its long-term drift, noise level, and effective resolution under in situ conditions at the seafloor are only known from a few published studies and for a few sensors. In this study we analyze 118 long-term seafloor pressure time series (longer than 2 months and up to a maximum time period of 9 years) to investigate effective resolution and long-term drift under in situ conditions. The data are from DART (NOAA, USA), IFM-GEOMAR (Germany), LOLEM (MAR monitoring project), and CORK (ODP/IODP) stations. Sensor drift is well described by an initial exponential part and a subsequent linear drift. In situ mean long-term drift is -0.88 ± 0.73 kPa/a, determined from all available data with a slight increase of drift with deployment depth. Unfortunately long-term sensor drift cannot be determined by short-term laboratory experiments before deployment nor predicted based on results from previous deployments. For the first time, we are able to quantify effective pressure resolution and drift of the widely used Paroscientific pressure gauges under in situ conditions, based on a large data base and numerous deployments. Our results provide important constrains for the interpretation of pressure records made with the Paroscientific sensors. Whereas relative resolution of the sensors is adequate to quantify transient seafloor and formation processes, long-term pressure changes caused by subsidence or uplift cannot be distinguished from sensor drift unless rates of vertical motion are large (tens of cm/yr). Therefore, in situ self-calibration procedures for the Paroscientific sensors are needed in order to benefit from the sensor's high effective resolution and long-term stability for the monitoring of geodynamic processes at the seafloor.

Villinger, H. W.; Polster, A.; Fabian, M.; Davis, E. E.

2011-12-01

404

Multiband analysis for colored amplitude-modulated ship noise  

Microsoft Academic Search

Propeller radiated cavitation noise is broadband yet audibly rhythmic, taking on the characteristics of amplitude-modulated noise. The study of this process is important because the shaft and blade rates, as well as other identifying features of the ship, can be inferred from the cavitation signal envelope. Unlike the conventional method for estimating the modulation frequency, this paper proposes a multirate

Pascal Clark; Ivars P. Kirsteins; Les E. Atlas

2010-01-01

405

A simplified Mach number scaling law for helicopter rotor noise  

Microsoft Academic Search

A simplified Mach number scaling law is obtained for rotational and high frequency broadband noise from helicopter rotors. These scaling laws are based on geometric parameters of the rotor. The existing theory of Lowson and Ollerhead is used in deriving the conventional Mt6 law for rotational noise of geometrically similar blades operating in similar flow environ. The effects of number

K. S. Aravamudan; A. Lee; W. L. Harris

1978-01-01

406

Augmentative and alternative communication: the role of broadband telecommunications  

Microsoft Academic Search

Explores a number of the communication advantages offered to nonspeaking disabled people by the advent of broadband telecommunications. The first section of the paper focuses on text messages created by the disabled person alone. Several different word-prediction techniques, employed by nonspeakers who find difficulty in typing at computer keyboards, are experimentally evaluated. The second section of the paper concentrates on

Andy McKinlay; William Beattie; J. L. Arnott; Nicolas A. Hine

1995-01-01

407

Social Network Theory, Broadband and the World Wide Web  

Microsoft Academic Search

This paper aims to predict some possible futures for the World Wide Web based on several key network parameters: size, complexity, cost and increasing connection speed thorough the uptake of broadband technology. This is done through the production of a taxonomy specifically evaluating the stability properties of the fully-connected star and complete networks, based on the Jackson and Wolinsky (1996)

D. Sgroi

2006-01-01

408

Rotary wing aerodynamically generated noise  

Microsoft Academic Search

The history and methodology of aerodynamic noise reduction in rotary wing aircraft are presented. Thickness noise during hover tests and blade vortex interaction noise are determined and predicted through the use of a variety of computer codes. The use of test facilities and scale models for data acquisition are discussed.

F. J. Schmitz; H. A. Morse

1982-01-01

409

Noise prevention  

NASA Astrophysics Data System (ADS)

Methods for noise abatement are discussed. Noise nuisance, types of noise (continuous, fluctuating, intermittent, pulsed), and types of noise abatement (absorption, vibration damping, isolation) are defined. Rockwool panels, industrial ceiling panels, baffles, acoustic foam panels, vibration dampers, acoustic mats, sandwich panels, isolating cabins and walls, ear protectors, and curtains are presented.

410

Active control of three-dimension impulsive scattered radiation based on a prediction method  

NASA Astrophysics Data System (ADS)

A method for predicting the scattered sound pressure induced by a three-dimension scatterer is proposed. This method is further used as an error sensing strategy in the active noise control (ANC) system for attenuating the three-dimension scattered radiation. Experiments are carried out to validate the prediction method, and a broadband feedforward ANC system combined with the given error sensing strategy is implemented to suppress an impulsive scattered sound pressure. It is found that the proposed ANC system based on the prediction method is effective, and about 8.2 dB attenuation of the scattered pressure is obtained at the observation point after the active control.

Han, Ning; Qiu, Xiaojun; Feng, Shengzhen

2012-07-01

411

Broadband Electromagnetic Pulses Coinciding with Sprite Luminosity  

NASA Astrophysics Data System (ADS)

This study reports novel optical sprite observations in southern France during the summer months 2009 and the associated electromagnetic radiation emitted in the frequency range >50 kHz. About 10% of the observed sprites are associated with consecutive pulses of >50 kHz electromagnetic radiation. Some of these broadband pulses occur simultaneously with the sprite luminosity. In particular, the electromagnetic radiation of the sprite itself can coincide with a broadband pulse. This behaviour is predicted by the relativistic runaway breakdown theory, in which the lightning electromagnetic field accelerates free electrons to form a narrow particle beam shooting upward into near-Earth space. This vertical relativistic runaway breakdown describes a novel physical process within the Earth's atmosphere, even though it may occur only on extremely rare occasions, i.e., ~100 upward particle beams per day around the globe. The wealth of currently planned future space missions in this research area will greatly enhance the detection likelihood of the predicted particle beams.

Fullekrug, M.; Roussel-Dupre, R. A.; Symbalisty, E.; Chanrion, O.; van der Velde, O. A.; Odzimek, A.; Whitley, T.; Neubert, T.

2009-12-01

412

Airport noise  

NASA Astrophysics Data System (ADS)

The problem of airport noise at several airports and air bases is detailed. Community reactions to the noise, steps taken to reduce jet engine noise, and the effect of airport use restrictions and curfews on air transportation are discussed. The adverse effect of changes in allowable operational noise on airport safety and altenative means for reducing noise pollution are considered. Community-airport relations and public relations are discussed.

Pendley, R. E.

413

Noise modeling, noise experiment, and noise inversion  

NASA Astrophysics Data System (ADS)

Recent developments in inverting ambient noise to obtain bottom reflection properties originated from an understanding of noise behavior and from noise modeling. Sea-surface noise can be modeled equivalently as a ray, wave, or mode phenomenon, but often the ray or flux approach provides the most insight (explaining, e.g., the noise-notch or low-frequency noise enhancement). Theoretically, noise vertical directionality is surprisingly sensitive to the effective depth of the sheet of sound sources, and this is borne out in the spread of behaviors found experimentally. A number of noise inversion approaches have been proposed based on coherence or directionality of sea-surface noise, individual ships or shipping, and airplane doppler. Using a drifting vertical array as a means to measure directionality, one can infer reflection coefficient versus angle and frequency. One can then use this directly for propagation calculation, or alternatively invert to geoacoustic parameters with the help of a fast noise model. A further development is to recover the reflection phase using spectral factorization, then Fourier transform to get the impulse response, which becomes a sub-bottom profile for a drifting array. At 4-kHz design frequency, the layer structure thus determined compares well with a boomer down to 15 m.

Harrison, Chris H.

2005-09-01

414

Adaptive noise  

PubMed Central

In biology, noise implies error and disorder and is therefore something which organisms may seek to minimize and mitigate against. We argue that such noise can be adaptive. Recent studies have shown that gene expression can be noisy, noise can be genetically controlled, genes and gene networks vary in how noisy they are and noise generates phenotypic differences among genetically identical cells. Such phenotypic differences can have fitness benefits, suggesting that evolution can shape noise and that noise may be adaptive. For example, gene networks can generate bistable states resulting in phenotypic diversity and switching among individual cells of a genotype, which may be a bet hedging strategy. Here, we review the sources of noise in gene expression, the extent to which noise in biological systems may be adaptive and suggest that applying evolutionary rigour to the study of noise is necessary to fully understand organismal phenotypes.

Viney, Mark; Reece, Sarah E.

2013-01-01

415

Effects of Cross-Sectional Dimensions on Active Noise Control in Rectangular and Round Ducts  

Microsoft Academic Search

Active noise control (ANC) works best to reduce low frequency noise. Because many industrial noise sources are broadband, ANC may be used more if it can be successfully applied to higher frequency ranges. This study explored one method to increase ANC effectiveness at higher frequencies. ANC is particularly useful in hard-walled ducts where plane waves propagate. Higher order mode waves

Jeremy M. Slagley; Steven Guffey

2007-01-01

416

Broadband cavity electromagnetically induced transparency  

SciTech Connect

Cavity electromagnetically induced transparency (EIT) is created in a three-level atomic system confined in a cavity and coupled to a free-space control laser and is manifested as a narrow transmission peak of a probe laser coupled into the cavity mode and tuned to the two-photon Raman resonance with the control laser. Cavity EIT can be observed with a control laser detuned from the atomic transition frequency in a range limited by the vacuum Rabi splitting of two cavity-atom normal modes. This leads to the broadband cavity EIT obtained in the coupled-cavity-atom system with a free-space, broadband control laser. We report an experimental observation of broadband cavity EIT in cold Rb atoms with a frequency-modulated control laser and discuss its application in multichannel and multifrequency light memory.

Wei Xiaogang [Department of Physics, Florida International University, Miami, Florida 33199 (United States); College of Physics, Jilin University, Changchun 130023 (China); Wang Yanhua [Department of Physics, Florida International University, Miami, Florida 33199 (United States); College of Physics and Electronics, Shanxi University, Taiyuan 030006 (China); Zhang Jiepeng [Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071 (China); Physics Division P-23, Los Alamos National Laboratory, Los Alamos, New Mexico 87544 (United States); Zhu Yifu [Department of Physics, Florida International University, Miami, Florida 33199 (United States)

2011-10-15

417

Performance analysis of adaptive OFDM system for Broadband Power Line Network  

Microsoft Academic Search

Power Line Network is proposed as an alternative for broadband data transmission especially in developing countries like India. The power line channel is affected by stochastic attenuation, multipath propagation and noise which can lead to the limitation of channel capacity and achievable data rate. One of the promising approaches to mitigate the problem is adaptive OFDM (AOFDM). Adaptive transmission methods

M. Rathinasabapathy; R. Nakkeeran

2012-01-01

418

Deep earthquake rupture histories determined by global stacking of broadband P waveforms  

Microsoft Academic Search

We conduct a systematic investigation of time histories of moment release in deep earthquakes, whose physical mechanism remains unknown. We have constructed source time functions (STFs) of 111 large deep earthquakes (depth >=100 km and Mw >= 6.4) by stacking P waveforms from broadband seismograms recorded by the Global Seismographic Network. Aligning and stacking waveforms cancels noise and allows us

Steven E. Persh; Heidi Houston

2004-01-01

419

Deep earthquake rupture histories determined by global stacking of broadband P waveforms  

Microsoft Academic Search

We conduct a systematic investigation of time histories of moment release in deep earthquakes, whose physical mechanism remains unknown. We have constructed source time functions (STFs) of 111 large deep earthquakes (depth ?100 km and Mw ? 6.4) by stacking P waveforms from broadband seismograms recorded by the Global Seismographic Network. Aligning and stacking waveforms cancels noise and allows us

Steven E. Persh; Heidi Houston

2004-01-01

420

Broadband ISDN architectures and technologies  

NASA Astrophysics Data System (ADS)

This paper brings together three concepts which together can be applied to tomorrow's broadband, mostly digital video, networks and services. These concepts are: high speed burst transmission of digital video from storage or service centers to local access or delivery networks, use of a ATM-threaded circuit switched paths for efficient transmission of blocks of digital video, and use of quadrature amplitude modulation methods to deliver digital video and data to the home, business or institution via fiber feeders and coaxial cable or twisted pair drops. Some business enabling factors and potential social implications of broadband services to the home are summarized.

Terry, Jack B.

1993-02-01

421

Noise in any frequency range can enhance information transmission in a sensory neuron  

NASA Astrophysics Data System (ADS)

The effect of noise on the neural encoding of broadband signals was investigated in the cricket cercal system, a mechanosensory system sensitive to small near-field air particle disturbances. Known air current stimuli were presented to the cricket through audio speakers in a controlled environment in a variety of background noise conditions. Spike trains from the second layer of neuronal processing, the primary sensory interneurons, were recorded with intracellular Electrodes and the performance of these neurons characterized with the tools of information theory. SNR, mutual information rates, and other measures of encoding accuracy were calculated for single frequency, narrowband, and broadband signals over the entire amplitude sensitivity range of the cells, in the presence of uncorrelated noise background also spanning the cells' frequency and amplitude sensitivity range. Significant enhancements of transmitted information through the addition of external noise were observed regardless of the frequency range of either the signal or noise waveforms, provided both were within the operating range of the cell. Considerable improvements in signal encoding were observed for almost an entire order of magnitude of near-threshold signal amplitudes. This included sinusoidal signals embedded in broadband white noise, broadband signals in broadband noise, and even broadband signals presented with narrowband noise in a completely non-overlapping frequency range. The noise related increases in mutual information rate for broadband signals were as high as 150%, and up to 600% increases in SNR were observed for sinusoidal signals. Additionally, it was shown that the amount of information about the signal carried, on average, by each spike was INCREASED for small signals when presented with noise-implying that added input noise can, in certain situations, actually improve the accuracy of the encoding process itself.

Levin, Jacob E.

1997-05-01

422

Underwater noise from offshore oil production vessels.  

PubMed

Underwater acoustic recordings of six Floating Production Storage and Offloading (FPSO) vessels moored off Western Australia are presented. Monopole source spectra were computed for use in environmental impact assessments of underwater noise. Given that operations on the FPSOs varied over the period of recording, and were sometimes unknown, the authors present a statistical approach to noise level estimation. No significant or consistent aspect dependence was found for the six FPSOs. Noise levels did not scale with FPSO size or power. The 5th, 50th (median), and 95th percentile source levels (broadband, 20 to 2500 Hz) were 188, 181, and 173 dB re 1 ?Pa @ 1 m, respectively. PMID:23742441

Erbe, Christine; McCauley, Robert; McPherson, Craig; Gavrilov, Alexander

2013-06-01

423

Implementation of diffraction in a ray-tracing model for the prediction of noise in open-plan offices.  

PubMed

Sound prediction in open-plan offices is a real challenge because of the complexity of the layout of such offices, and therefore because of the multitude of acoustic phenomena involved. One such phenomenon, of primary importance, and not the least challenging of them, is the diffraction by screens and low dividers that usually partition the workspace. This paper describes implementing the equations of the Uniform Theory of Diffraction [McNamara et al. (1990). Introduction to the Uniform Theory of Diffraction (Artech House, Boston)] in an existing ray-tracing model initially dedicated to sound prediction in industrial premises. For the purposes of validation, a series of measurements was conducted in a semi-anechoic chamber in the same manner as Wang and Bradley [(2002). Appl. Acoust. 63, 849-866] but including real desktops instead of single screens. A first phase was dedicated to controlling the quality of the installation by making comparisons with McNamara's solution for a single screen on a rigid floor. Then, the validation itself was conducted with measurements on real desktops, first without a ceiling, and then with a rigid ceiling suspended above the double desk. The results of the comparisons between calculations and measurements in this configuration have demonstrated that the model is an effective tool for predicting sound levels in an open-plan office. PMID:23145598

Chevret, P; Chatillon, J

2012-11-01

424

Traceability methods comparison of broadband UV radiometers  

NASA Astrophysics Data System (ADS)

Broadband UV radiometers are widely used for measuring UV irradiance or radiant exposure in various areas of health, industry, and science, such as in weather aging of materials, semiconductor lithography, non-destructive testing, UV curing, catalytic process, environmental monitoring, atmospheric research, water purification, medical diagnostics and therapy, space-based astrophysical observations and other applications. The accuracy of measurement is influenced by many factors such as the characteristics of the radiometer, operating conditions, environmental conditions and the UV sources to be measured. Due to the lack of spectral resolving power, significant measurement errors may occur if the radiometer has poor quality. Five different calibration and traceability methods of UV radiometers were realized and analyzed at National Institute of Metrology (NIM), including absolute spectral irradiance method based on standard lamps, absolute spectral power responsivity method of detectors, absolute thermoelectric radiometer method, electrically calibrated pyroelectric radiometer method and method of comparing with the standard radiometer. The above methods were used to realize the irradiance responsivity of a broadband UVA meter independently. Compared to absolute spectral irradiance method based on standard lamps, relative deviation of these traceability methods are 0%, 0.18%, 2.50%, -3.04% and 4.11% respectively. Absolute spectral power responsivity method of detectors is adopted by the most national metrology institute to realize UV irradiance responsivity. The deviation of absolute thermoelectric radiometer method results from poor signal-to-noise of the combination of radiation source and a UV filter, near to the sensitivity limit of the absolute radiometer. The largest deviation of method of comparing with the standard radiometer comes from different response wavelength, different receiving area between the standard radiometer and the test radiometer. Spectral irradiance method based on standard lamps is the principal traceability method of NIM tracing to the national spectral irradiance primary standard directly. This method was proved by international comparison of "Irradiance Responsivity of UVA Detectors APMP PR-S1". The comparison results showed that the consistency between the NIMs' value and the international reference one is the best among the seven participants. On the basis of the above theories and methods, the uncertainty of broadband ultraviolet irradiance standard under the defined conditions was cut down to 2.0% (k=1) from 10% (k=1).

Dai, Caihong; Huang, Bo; Wu, Zhifeng; Ouyang, Huiquan; Yu, Jialin

2011-11-01

425

How broadband changes online and offline behaviors  

Microsoft Academic Search

Using longitudinal panel data on Internet subscriptions and online and offline activities, I assess how broadband adoption affects behavior. Consistent with previous research, this study finds that broadband adopters increase their overall Internet usage. However, broadband adoption is associated with an increase in relatively few specific applications, like downloading music and online purchasing. Among “socially desirable” activities that governments seek

Jed Kolko

2010-01-01

426

Networked Nation: Broadband in America, 2007  

ERIC Educational Resources Information Center

|This report highlights the dramatic growth of broadband in the United States. The report shows that the Administration's technology, regulatory and fiscal policies have stimulated innovation and competition, and encouraged investment in the U.S. broadband market contributing to significantly increased accessibility of broadband services. The…

National Telecommunications and Information Administration, 2008

2008-01-01

427

The role of government in broadband access  

Microsoft Academic Search

This paper discusses the role of governments in broadband. It is divided into five sections. Following an introduction in section one, section two discusses the diffusion of broadband Internet. Section three deals with competition-based and public-goods views on regulation and the corresponding roles and issues for governments. To gain deeper insights into the role of government in broadband, section four

Arnold Picot; Christian Wernick

2007-01-01

428

Noise generation in axial flow fans  

Microsoft Academic Search

An empirical equation for fan noise is presented. The equation predicts, with fair accuracy, the noise of several fan configurations tested, yielding noise spectra over the frequency range 40 to 10,000 Hz at various fan speeds and over the measurable range of fan performance characteristics. The ``discrete'' parts of the fan noise are considered in terms of a ``resonance'' phenomenon

C. G. van Niekerk

1966-01-01

429

Traffic models in broadband networks  

Microsoft Academic Search

Traffic models are at the heart of any performance evaluation of telecommunications networks. An accurate estimation of network performance is critical for the success of broadband networks. Such networks need to guarantee an acceptable quality of service (QoS) level to the users. Therefore, traffic models need to be accurate and able to capture the statistical characteristics of the actual traffic.

A. Adas

1997-01-01

430

Broadband Reciprocal Ferrite Phase Shifters  

Microsoft Academic Search

Broadband ferrite phase shifters were constructed in X band waveguide by locating wide ferrite slabs along the center line of the broad waveguide wall and applying a longitudinal magnetic field. The bandwidth of these phase shifters was optimized through proper selection of ferrite dimensions and the amount of dielectric loading or by an appropriate choice of guiding structure. The relative

T. D. Geiszler; R. A. Henschke

1960-01-01

431

Socioeconomic determinants of broadband adoption  

Microsoft Academic Search

Purpose – As innovative forms of information and communication technologies (ICTs) such as broadband internet are being adopted, the equitable distribution of ICTs has become an issue of concern. These apprehensions are being attributed to social exclusion that could arise due to the limited internet use among citizens with lower incomes or educational levels. This research aims to examine the

Yogesh Kumar Dwivedi; Banita Lal

2007-01-01

432

Resource allocation for broadband networks  

Microsoft Academic Search

The major benefit of a broadband integrated ATM (asynchronous transfer mode) network is flexible and efficient allocation of communications bandwidth for communications services. However, methods are needed for evaluating congestion for integrated traffic. The author suggests evaluating congestion at different levels, namely the packet level, the burst level, and the call level. Congestion is measured by the probabilities of packet

J. Y. Hui

1988-01-01

433

Broad-Band Directional Couplers  

Microsoft Academic Search

It is shown how to connect two identical hybrids to obtain a directional coupler of arbitrary power division that operates over a broader band than that of the components. The broad-banding technique is possible with a certain kind of hybrid that includes Riblet couplers, multihole hybrids, coaxial hybrids and semioptical hybrids, but excludes T hybrids and ring hybrids. Riblet couplers

E. A. Marcatili; D. H. Ring

1962-01-01

434

A Broadband Accelerator Control Network  

Microsoft Academic Search

A broadband data communications network has been implemented at BNL for control of the Alternating Gradient Synchrotron (AG) proton accelerator, using commercial CATV hardware, dual coaxial cables as the communications medium, and spanning 2.0 km. A 4 MHz bandwidth Digital Control channel using CSMA-CA protocol is provided for digital data transmission, with 8 access nodes available over the length of

J. Skelly; T. Clifford; R. Frankel

1983-01-01

435

Community noise  

NASA Astrophysics Data System (ADS)

Airport and community land use planning as they relate to airport noise reduction are discussed. Legislation, community relations, and the physiological effect of airport noise are considered. Noise at the Logan, Los Angeles, and Minneapolis/St. Paul airports is discussed.

Bragdon, C. R.

436

Quantum noise in VCSELs  

NASA Astrophysics Data System (ADS)

In this paper, we study in detail the intensity noise characteristics of vertical-cavity surface-emitting lasers (VCSELs). We demonstrate the possibility of generating intensity squeezed light with free-running or injection-locked VCSELs. Sub-shot noise operation results from very strong anticorrelations between the transverse modes. These anticorrelations have also been analysed through the transverse spatial distribution of the intensity noise. In the case of two transverse modes above threshold, our experimental results are found to be in good agreement with the predictions of a phenomenological model.

Hermier, J.-P.; Maurin, I.; Giacobino, E.; Schnitzer, P.; Michalzik, R.; Ebeling, K. J.; Bramati, A.; Khoury, A. Z.

2000-10-01

437

Underwater noise of small personal watercraft (jet skis).  

PubMed

Personal watercraft (water scooters, jet skis) were recorded under water in Bramble Bay, Queensland, Australia. Underwater noise emissions consisted of broadband energy between 100 Hz and 10 kHz due to the vibrating bubble cloud generated by the jet stream, overlain with frequency-modulated tonals corresponding to impeller blade rates and harmonics. Broadband monopole source levels were 149, 137, and 122 dB re 1 ?Pa @ 1 m (5th, 50th, and 95th percentiles). Even though these are lower than those of small propeller-driven boats, it is not necessarily the broadband source level that correlates with the bioacoustic impact on marine fauna. PMID:23556699

Erbe, Christine

2013-04-01

438

A Highly Linear Broadband Variable Gain LNA for TV Applications  

Microsoft Academic Search

A broadband variable-gain low noise amplifier with triple output for TV tuners has been demonstrated in a 0.18 mum SiGe technology. The gain varies continuously from 27 dB to -28 dB and has better than 1 dB precision over a 1GHz bandwidth. At 27 dB gain the amplifier shows 6.5 dB NF, 82 dBmV OIP3 and 121 dBmV OIP2. OIP3

D. Manstretta; L. Dauphinee

2007-01-01

439

Stochastic Resonance Improves Broadband Encoding in the Cricket Cercal System.  

NASA Astrophysics Data System (ADS)

In any physical or biological system a certain amount of environmental noise is unavoidable, and the information therein irrelevant to the organism. Traditionally in signal analysis noise is considered detrimental to the process of signal encoding, and merely a necessary evil to be avoided. It has been observed recently, however, that in some nonlinear systems power from random input noise actually improves the output signal-to-noise ratio (SNR) over a limited operating range, particularly near threshold. This effect is known as stochastic resonance (SR). By taking advantage of SR during the neural encoding process, a cell can optimize its information flow properties. Previous experimental work in SR has investigated only the coding of sinusoidal signals embedded in a broadband white noise background. In this work we demonstrate SR for not only the sine wave case, but also for extended bandwidth stimuli in the presence of white noise, and for cases in which the signal and white noise background frequency spectra are completely non-overlapping. We have investigated the effects of noise on information transfer in the cricket cercal system, a mechanosensory system sensitive to small near-field air particle disturbances, by presenting known wind stimuli to the cricket through audio speakers in a controlled environment along with varying levels of uncorrelated white noise background air current. Spike trains from the second layer of neuronal processing, the primary sensory interneurons, were recorded with intracellular electrodes with the signal and noise presented along the cell's preferred direction. Through the statistical techniques of Shannon's information theory we quantified the amount of information contained in the elicited spike trains about the signal in the various noise environments, as well as the SNR and other measures of the encoding process. An enhancement of output SNR was observed over the entire frequency operating range of the neurons, for almost an entire order of magnitude of near-threshold signal amplitudes. Additionally, we found that the amount of information about the signal carried, on average, by each spike was INCREASED for small signals when presented with noise - implying that added input noise can, in certain situations, actually improve the accuracy of the encoding process itself.

Levin, Jacob

1996-03-01

440

Assessing broadband vegetation indices and QuickBird data in estimating leaf area index of corn and potato canopies  

Microsoft Academic Search

Leaf area index (LAI) is a key biophysical variable that can be used to derive agronomic information for field management and yield prediction. In the context of applying broadband and high spatial resolution satellite sensor data to agricultural applications at the field scale, an improved method was developed to evaluate commonly used broadband vegetation indices (VIs) for the estimation of

Jindong Wu; Dong Wang; Marvin E. Bauer

2007-01-01

441

Influence of the Sampling Rate and Noise Characteristics on Prediction of the Maximal Safe Laser Exposure in Human Skin Using Pulsed Photothermal Radiometry  

NASA Astrophysics Data System (ADS)

Pulsed photothermal radiometry (PPTR) allows for noninvasive determination of the laser-induced temperature depth profile in strongly scattering samples, including human skin. In a recent experimental study, we have demonstrated that such information can be used to derive rather accurate predictions of the maximal safe radiant exposure on an individual patient basis. This has important implications for efficacy and safety of several laser applications in dermatology and aesthetic surgery, which are often compromised by risk of adverse side effects (e.g., scarring, and dyspigmentation) resulting from nonselective absorption of strong laser light in epidermal melanin. In this study, the differences between the individual maximal safe radiant exposure (H_{max}) values as predicted from PPTR temperature depth profiling performed using a commercial mid-IR thermal camera (as used to acquire the original patient data) and our customized PPTR setup are analyzed. To this end, the latter has been used to acquire 17 PPTR records from three healthy volunteers, using 1 ms laser irradiation at 532 nm and a signal sampling rate of 20 000 s^{-1}. The laser-induced temperature profiles are reconstructed first from the intact PPTR signals, and then by binning the data to imitate the lower sampling rate of the IR camera (1000 fps). Using either the initial temperature profile in a dedicated numerical model of heat transfer or protein denaturation dynamics, the predicted levels of epidermal thermal damage (\\varOmega ) and the corresponding H_{max} are compared. A similar analysis is performed also with regard to the differences between noise characteristics of the two PPTR setups.

Vidovi?, L.; Milani?, M.; Majaron, B.

2013-05-01

442

Fan Noise: A Challenge to CAA  

Microsoft Academic Search

The objective of this paper is to expose the computational aeroacoustics (CAA) community to the current unresolved issues in modeling and predicting fan noise. The paper includes a description of the sources of fan noise and a discussion of the current status of the fan noise prediction methods and their shortcomings. The discussion is focused on the issues and includes

Edmane Envia; Alexander G. Wilson; Dennis L. Huff

2004-01-01

443

Computational simulation of rotating noise of fan  

Microsoft Academic Search

consists of shaft frequency, blade passage frequency (BPF) and their higher harmonics. The shaft-order noise, which is mainly induced by unbalanced rotating, is often hard to be eliminated. In this paper, the rotating noise caused by geometric asymmetry is discussed and predicted. Analytic point force model is firstly used to predict the noise at points in different directions. Then a

Tao Feng; Jing Wang; Bin Liu; Nan Li; Xue Wu

2011-01-01

444

Broadband network selection issues  

NASA Astrophysics Data System (ADS)

Selecting the best network for a given cable or telephone company provider is not as obvious as it appears. The cost and performance trades between Hybrid Fiber Coax (HFC), Fiber to the Curb (FTTC) and Asymmetric Digital Subscriber Line networks lead to very different choices based on the existing plant and the expected interactive subscriber usage model. This paper presents some of the issues and trades that drive network selection. The majority of the Interactive Television trials currently underway or planned are based on HFC networks. As a throw away market trial or a short term strategic incursion into a cable market, HFC may make sense. In the long run, if interactive services see high demand, HFC costs per node and an ever shrinking neighborhood node size to service large numbers of subscribers make FTTC appear attractive. For example, thirty-three 64-QAM modulators are required to fill the 550 MHz to 750 MHz spectrum with compressed video streams in 6 MHz channels. This large amount of hardware at each node drives not only initial build-out costs, but operations and maintenance costs as well. FTTC, with its potential for digitally switching large amounts of bandwidth to an given home, offers the potential to grow with the interactive subscriber base with less downstream cost. Integrated telephony on these networks is an issue that appears to be an afterthought for most of the networks being selected at the present time. The major players seem to be videocentric and include telephony as a simple add-on later. This may be a reasonable view point for the telephone companies that plan to leave their existing phone networks untouched. However, a phone company planning a network upgrade or a cable company jumping into the telephony business needs to carefully weigh the cost and performance issues of the various network choices. Each network type provides varying capability in both upstream and downstream bandwidth for voice channels. The noise characteristics vary as well. Cellular quality will not be tolerated by the home or business consumer. The network choices are not simple or obvious. Careful consideration of the cost and performance trades along with cable or telephone company strategic plans is required to ensure selecting the best network.

Leimer, Michael E.

1996-01-01

445

A new model for the prediction of turbofan noise with the effect of locally and non-locally reacting liners  

NASA Astrophysics Data System (ADS)

This paper presents a unified model to study the effect of both locally and non-locally reacting liners on the sound radiation generated by fan blade rotating sources. This model is set up by the following steps. First, the spinning mode eigenfunction expansions are used to obtain the solution of sound field inside the duct, while the effect of duct liner is modeled by distributed monopole sources, thus effectively avoiding the solution of a difficult complex eigenvalue problem. Secondly, in order to avoid the estimation of the generalized impedances at the inlet and exhaust planes, a boundary element method is used to give the solution outside the duct. With the suitable boundary conditions imposed on the inlet and exhaust planes, a matrix equation is obtained, and the relevant numerical calculation shows this model can not only give a good agreement with existing results for locally reacting liner but also has a capability to predict the sound radiation from fan rotating blade sources with an arbitrary combination of locally and non-locally reacting liners.

Sun, Xiaofeng; Wang, Xiaoyu; Du, Lin; Jing, Xiaodong

2008-09-01

446

Characteristics of broadband underwater transducers integrated with tuning coils and cables  

Microsoft Academic Search

An application of a method to determine the characteristics of an integrated system using measured characteristics of the subsystems is presented. The method is used to predict the characteristics of broadband underwater transducers concatenated with tuning coils and long cables. The effect of measurement errors on the predicted characteristics of the integrated transducer is implicitly studied by comparing predicted and

R. Ramesh; S. S. Pillai; P. Abraham; D. D. Ebenezer

2009-01-01

447

Experimental generation of broadband quadrature entanglement using laser pulses  

SciTech Connect

We report on the generation of broadband pulsed quadrature entanglement by combining two squeezed vacua, which are generated from two degenerate optical parametric amplifiers (OPAs), on a beam splitter. With a single pass through OPA, in which a periodically poled lithium niobate waveguide is used as a nonlinear material, the noise reduction of 3.4{+-}0.2 dB below the shot noise limit is observed with a bandwidth of more than 200 MHz. The entanglement correlation or EPR correlation is confirmed with a sufficient criterion <{delta}{sup 2}(X{sub a}+X{sub b})>+<{delta}{sup 2}(Y{sub a}-Y{sub b})>=1.28<2.

Zhang, Yun; Furuta, Tatsuya; Okubo, Ryuhi; Takahashi, Kosuke; Hirano, Takuya [Department of Physics, Gakushuin University, 1-5-1 Mejiro, Toshima-ku, Tokyo, 171-8588, Japan CREST, Japan Science and Technology Agency, 1-9-9 Yaesu, Chuo-ku, Tokyo, 103-0028 (Japan)

2007-07-15

448

MOBB: Data Analysis from an Ocean Floor Broadband Seismic Observatory  

NASA Astrophysics Data System (ADS)

MOBB (Monterey bay Ocean floor Broad Band project) is a collaborative project between the Monterey Bay Aquarium Research Institute (MBARI) and the Berkeley Seismological Laboratory (BSL). Its goal is to install and operate a permanent seafloor broadband station as a first step towards extending the on-shore broadband seismic network in northern California, to the seaside of the North-America/Pacific plate boundary, providing improved azimuthal coverage for regional earthquake and structure studies. The MOBB station was installed on the seafloor in Monterey Bay, 40 km offshore, and at a depth of 1000m from the sea surface, in April 2002, and is completely buried under the seafloor level. The installation made use of MBARI's Point Lobos ship and ROV Ventana and the station currently records data autonomously. Dives are scheduled regularly (about every three months) to recover and replace the recording and battery packages. Some data were lost in the first half of 2003 due to hardware and software problems in the recording system. The ocean-bottom MOBB station currently comprises a three-component seismometer package (Guralp CMG-1T), a current-meter, a digital pressure gauge (DPG), and recording and battery packages. The seismometer package is mounted on a cylindrical titanium pressure vessel 54cm in height and 41 cm in diameter, custom built by the MBARI team and outfitted for underwater connection. Since the background noise in the near-shore ocean floor environment is high in the band pass of interest, for the study of regional and teleseismic signals, an important focus of this project is to develop methods to a posteriori increase signal to noise ratios, by deconvolving contributions from various sources of noise. We present results involving analysis of correlation of background noise with tide, ocean current and pressure records, combining data from MOBB and regional land based stations of the Berkeley Digital Seismic Network (BDSN). We also present preliminary results of modeling of the signal generated noise due to reverberation in the near surface sedimentary pile. The experience gained in MOBB will be valuable, in particular, for future long term or temporary deployments of buried broad-band seismometers such as are envisaged in the context of the Ocean Mantle Dynamics Initiative.

Uhrhammer, R. A.; Dolenc, D.; Romanowicz, B.; Stakes, D.; McGill, P.; Neuhauser, D.; Ramirez, T.

2003-12-01

449

Enhanced propagation modeling of directional aviation noise: A hybrid parabolic equation-fast field program method  

NASA Astrophysics Data System (ADS)

Commercial air traffic is anticipated to increase rapidly in the coming years. The impact of aviation noise on communities surrounding airports is, therefore, a growing concern. Accurate prediction of noise can help to mitigate the impact on communities and foster smoother integration of aerospace engineering advances. The problem of accurate sound level prediction requires careful inclusion of all mechanisms that affect propagation, in addition to correct source characterization. Terrain, ground type, meteorological effects, and source directivity can have a substantial influence on the noise level. Because they are difficult to model, these effects are often included only by rough approximation. This dissertation presents a model designed for sound propagation over uneven terrain, with mixed ground type and realistic meteorological conditions. The model is a hybrid of two numerical techniques: the parabolic equation (PE) and fast field program (FFP) methods, which allow for physics-based inclusion of propagation effects and ensure the low frequency content, a factor in community impact, is predicted accurately. Extension of the hybrid model to a pseudo-three-dimensional representation allows it to produce aviation noise contour maps in the standard form. In order for the model to correctly characterize aviation noise sources, a method of representing arbitrary source directivity patterns was developed for the unique form of the parabolic equation starting field. With this advancement, the model can represent broadband, directional moving sound sources, traveling along user-specified paths. This work was prepared for possible use in the research version of the sound propagation module in the Federal Aviation Administration's new standard predictive tool.

Rosenbaum, Joyce E.

450

Bringing "True" Broadband to America  

SciTech Connect

The United States has sunk to 10th place worldwide in broadband deployment, and the current and foreseeable bandwidth offerings of the major American telephone and cable providers are woefully inadequate to support the nation's future bandwidth needs. A century ago, when the private power companies focused on electrifying large population centers and left most of the nation literally in the dark, thousands of communities formed their own electric utilities and thrived, while others that did not became 'ghost towns.' Several major cities also formed municipal electric utilities that cut power prices in half while significantly improving service quality. Jim Baller, a national leader in the community broadband movement, will discuss the role that local governments, educational institutions, the scientific community, and others can play today to help America break through its bandwidth bottleneck.

Baller, Jim (Baller Herbst Law Group)

2004-07-21

451

NASA's Vision for Jet Noise Engineering.  

National Technical Information Service (NTIS)

Until recently, the design of jet engines for quiet operation was limited by engineers' ability to predict the jet noise generated by a nozzle exhaust system. More importantly, the 'intermediate steps' between nozzle design and noise had not been understo...

K. W. Kinzie B. S. Henderson J. E. Bridges

2004-01-01

452

The many paradoxes of broadband  

Microsoft Academic Search

Thereismuchdismayandevendespairovertheslowpaceatwhichbroadbandisadvanc- ing in the United States. This slow pace is often claimed to be fatally retarding the recovery of the entire IT industry. As a result there are increasing calls for government action, through regulation oreven throughoutrightsubsidies. A careful examination shows that broadband is full of puzzles and paradoxes, which suggests cautionbeforetakinganydrasticaction.Asonesimpleexample,thebasicmeaningofbroadbandis almostuniversally misunderstood, sincebytheo-cial deflnition, weall havebroadbandcourtesyof thepostalsystem.Also,broadbandpenetration,whilegenerallyregardedasdisappointinglyslow,is actually

Andrew M. Odlyzko

2003-01-01

453

FAST Copper For Broadband Access  

Microsoft Academic Search

This is an overview of the ongoing FAST Copper project, which is aimed at substantial improvements in rate, reach, reliability, and quality in copper-last-mile broadband access through fiber\\/DSL deployment, engineering innovations, and fundamental research. The project is funded by NSF, and is currently pursued jointly by Princeton University, Stanford University, and Fraser Research Lab. In this article, we out- line

Mung Chiang; Jianwei Huang; Dahai Xu; Yung Yi; Chee Wei Tan; Raphael Cendrillon

454

AERONAUTICAL BROADBAND COMMUNICATIONS VIA SATELLITE  

Microsoft Academic Search

The paper discusses various aspects of aeronautical broadband satellite communications (AirCom). A range of applications and services is identified and categorized into the scenarios of in-flight entertainment, in-flight office, telemedicine, flight security, and flight logistics & maintenance. A number of operational and planned AirCom systems are presented. A structured overview of key issues and respective steps for the system design

M. Werner; M. Holzbock

455

Broad-Band Systems Standards  

Microsoft Academic Search

The broad-band communications industry is small and fractionated (about 3100 cable television systems serving 8.5 million subscribers in the U.S.), but has a high potential for growth by offering a wide variety of communications services. If this large number of systems is to collectively provide nationwide services, performance and interconnection standards will be essential. In this paper we note relevant

R. Powers

1975-01-01

456

Broadband light scattering of glycerol  

Microsoft Academic Search

The broadband light scattering spectra of glycerol were measured by the use of both the Sandercook-type 3+3 pass vernier tandem Fabry=Perot interferometer and the triple-grating additive spectrometer. The VH spectrum at 363K clearly shows ? and ? peaks. In the VV spectra the strong viscoelastic coupling between acoustic phonon and a relaxation process was observed. It is found that the

S. Kojima; K. Takanashi; A. Yoshiwara

1995-01-01

457

Assessment and evaluation of noise controls on roof bolting equipment and a method for predicting sound pressure levels in underground coal mining  

Microsoft Academic Search

Over-exposure to noise remains a widespread and serious health hazard in the U.S. mining industries despite 25 years of regulation. Every day, 80% of the nation's miners go to work in an environment where the time weighted average (TWA) noise level exceeds 85 dBA and more than 25% of the miners are exposed to a TWA noise level that exceeds

Rudy J. Matetic

2006-01-01

458

Noise contaminated transmittance  

SciTech Connect

The authors compare the efficiency of a classifier based on probabilistic neural networks and the general least squares method. Both methods must accommodate noise due to uncertainty in the measured spectrum at each wavelength. The evaluation of both methods is based on a simulated transmittance spectrum, in which the received signal is supplemented by an additive admixture of noise. To obtain a re